ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Other Sources  (968)
  • Astrophysics  (967)
  • Animals
  • 2015-2019  (963)
  • 1980-1984  (5)
  • 1
    facet.materialart.
    Unknown
    Niphargus-Thiothrix associations may be widespread in sulphidic groundwater ecosystems: evidence from southeastern Romania. (2018)
    Details
    Publication Date: 2021-04-25
    Description: Niphargus is a speciose amphipod genus found in groundwater habitats across Europe. Three Niphargus species living in the sulphidic Frasassi caves in Italy harbour sulphur-oxidizing Thiothrix bacterial ectosymbionts. These three species are distantly related, implying that the ability to form ectosymbioses with Thiothrix may be common among Niphargus. Therefore, Niphargus-Thiothrix associations may also be found in sulphidic aquifers other than Frasassi. In this study, we examined this possibility by analysing niphargids of the genera Niphargus and Pontoniphargus collected from the partly sulphidic aquifers of the Southern Dobrogea region of Romania, which are accessible through springs, wells and Movile Cave. Molecular and morphological analyses revealed seven niphargid species in this region. Five of these species occurred occasionally or exclusively in sulphidic locations, whereas the remaining two were restricted to nonsulphidic areas. Thiothrix were detected by PCR on all seven Dobrogean niphargid species and observed using microscopy to be predominantly attached to their hosts' appendages. 16S rRNA gene sequences of the Thiothrix epibionts fell into two main clades, one of which (herein named T4) occurred solely on niphargids collected in sulphidic locations. The other Thiothrix clade was present on niphargids from both sulphidic and nonsulphidic areas and indistinguishable from the T3 ectosymbiont clade previously identified on Frasassi-dwelling Niphargus. Although niphargids from Frasassi and Southern Dobrogea are not closely related, the patterns of their association with Thiothrix are remarkably alike. The finding of similar Niphargus-Thiothrix associations in aquifers located 1200 km apart suggests that they may be widespread in European groundwater ecosystems.
    Keywords: amphipods; ecology; sulphide; symbiosis; systematics; taxonomy ; 551 ; Amphipoda ; Animals ; DNA, Bacterial ; Ecosystem ; Groundwater ; Molecular Sequence Data ; Phylogeny ; RNA, Ribosomal, 16S ; Romania ; Sequence Analysis, DNA ; Sulfur ; Symbiosis ; Thiothrix
    Language: English , English
    Type: article , publishedVersion
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 2
    facet.materialart.
    Unknown
    On the Fragmentation of Rotating Interstellar Clouds (1981)
    In:  CASI
    Details
    Publication Date: 2005-11-09
    Description: Simple physical arguments are used to estimate the time scale for fragmentation of a collapsing, rotating, isothermal, interstellar cloud. This time scale is compared with a similarly estimated time scale for the collapse upon itself of a transitory ring structure. It is shown to be plausible for a cloud with a given ratio of rotational to gravitational energy (beta) that as the ratio of thermal to gravitational energy (alpha) is varied, there is an intermediate range of alpha where a ring forms and collapses on itself, prior to fragmentation. For higher or lower alpha however, the cloud fragments prior to ring self-collapse. The analysis is compared with the results of numerical multidimensional, gravitational, hydrodynamical collapse and shown to be in good agreement with them.
    Keywords: Astrophysics
    Type: Astrophysical Journal; Volume 244; 40-44
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 3
    facet.materialart.
    Unknown
    Behavior of Molecules on Interstellar Grains: Application of the Langevin Equation and Iterative Extended Huckel (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-23
    Description: The Langevin equation was used to explore an adsorbate desorption mechanism. Calculations were performed using iterative extended Huckel on a silica model site with various small adsorbates, e.g., H, CH, OH, NO, CO. It was found that barriers to free traversal from one site to another are substantial (approximately 3 - 10 eV). A bootstrap desorption mechanism for some molecules in the process of forming at a site also became apparent from the calculations. The desorption mechanisms appear to be somewhat balanced by a counterforce--the attraction of sites for the newly desorbed molecule. The order of attraction to a silica grain site for the diatomic molecules considered was OH 〉 CH 〉 CO 〉 NO, when these entities were sufficiently distant. The nature of the silica grain and that of the "cold" desorption mechanism, when considered together, suggest that the abundance of very small grains might be less common than anticipated.
    Keywords: Astrophysics
    Type: Astrophysical Journal; Volume 242; 149-164
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 4
    facet.materialart.
    Unknown
    A Heuristic Criterion for Instability to Fragmentation in Rotating, Interstellar Clouds (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-23
    Description: A heuristic criterion, based on linear perturbation analysis, is applied to the initial growth of density perturbations in isothermal or adiabatic gas clouds, with initially uniform density and uniform rotation. The heuristic criterion is shown to be consistent with the available results from numerical calculations of cloud collapse. The criterion predicts that perturbations varying as cos (m(phi)) will be most likely to grow when )pi is small, unless the cloud is nearly pressureless.
    Keywords: Astrophysics
    Type: Astrophysical Journal (ISSN 0004-637X); Volume 259; 159-165
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 5
    facet.materialart.
    Unknown
    Su Lyncis, a Hard X-Ray Bright M Giant: Clues Point to a Large Hidden Population of Symbiotic Stars (2016)
    In:  Other Sources
    Details
    Publication Date: 2017-05-23
    Description: Symbiotic star surveys have traditionally relied almost exclusively on low resolution optical spectroscopy. However, we can obtain a more reliable estimate of their total Galactic population by using all available signatures of the symbiotic phenomenon. Here we report the discovery of a hard X-ray source, 4PBC J0642.9+5528, in the Swift hard X-ray all-sky survey, and identify it with a poorly studied red giant, SU Lyn, using pointed Swift observations and ground-based optical spectroscopy. The X-ray spectrum, the optical to UV spectrum, and the rapid UV variability of SU Lyn are all consistent with our interpretation that it is a symbiotic star containing an accreting white dwarf. The symbiotic nature of SU Lyn went unnoticed until now, because it does not exhibit emission lines strong enough to be obvious in low resolution spectra. We argue that symbiotic stars without shell-burning have weak emission lines, and that the current lists of symbiotic stars are biased in favor of shell-burning systems. We conclude that the true population of symbiotic stars has been underestimated, potentially by a large factor.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN41432 , Monthly Notices of the Royal Astronomical Society (ISSN 0035-8711; e-ISSN 1365-8711); Volume 461; No. 1; L1-L5
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 6
    facet.materialart.
    Unknown
    Identification of the Hard X-Ray Source Dominating the E 〉 25 keV Emission of the Nearby Galaxy M31 (2017)
    In:  Other Sources
    Details
    Publication Date: 2017-05-02
    Description: We report the identification of a bright hard X-ray source dominating the M31 bulge above 25 keV from a simultaneous NuSTAR-Swift observation. We find that this source is the counterpart to Swift J0042.6+4112, which was previously detected in the Swift BAT All-Sky Hard X-Ray Survey. This Swift BAT source had been suggested to be the combined emission from a number of point sources; our new observations have identified a single X-ray source from 0.5 to 50 keV as the counterpart for the first time. In the 0.5-10 keV band, the source had been classified as an X-ray Binary candidate in various Chandra and XMM-Newton studies; however, since it was not clearly associated with Swift J0042.6+4112, the previous E is less than 10keVobservations did not generate much attention. This source has a spectrum with a soft X-ray excess (kT approximately equal to 0.2 keV) plus a hard spectrum with a power law of gamma approximately equal to 1 and a cutoff around 15-20 keV, typical of the spectral characteristics of accreting pulsars. Unfortunately, any potential pulsation was undetected in the NuSTAR data, possibly due to insufficient photon statistics. The existing deep HST (Hubble Space Telescope) images exclude high-mass (greater than 3 times the radius of the moon) donors at the location of this source. The best interpretation for the nature of this source is an X-ray pulsar with an intermediate-mass (less than 3 times the radius of the moon M) companion or a symbiotic X-ray binary. We discuss other possibilities in more detail.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN41428 , The Astrophysical Journal (ISSN 0004-637X; e-ISSN 1538-4357); Volume 838; No. 1; 47
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 7
    facet.materialart.
    Unknown
    Performance of the PRAXyS X-Ray Polarimeter (2016)
    In:  Other Sources
    Details
    Publication Date: 2017-04-29
    Description: The performance of the Time Projection Chamber (TPC) polarimeter for the Polarimeter for Relativistic Astrophysical X-ray Sources (PRAXyS) Small Explorer was evaluated using polarized and unpolarized X-ray sources. The PRAXyS mission will enable exploration of the universe through X-ray polarimetry in the 2-10 keV energy band. We carried out performance tests of the polarimeter at the Brookhaven National Laboratory, National Synchrotron Light Source (BNL-NSLS) and at NASA's Goddard Space Flight Center. The polarimeter was tested with linearly polarized, monochromatic X-rays at 11 different energies between 2.5 and 8.0 keV. At maximum sensitivity, the measured modulation factors at 2.7, 4.5 and 8.0 keV are 27%, 43% and 59%, respectively and the measured angle of polarization is consistent with the expected value at all energies. Measurements with a broadband, unpolarized X-ray source placed a limit of less than 1% on false polarization in the PRAXyS polarimeter.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN41158 , Nuclear Instruments and Methods in Physics Research A (ISSN 0168-9002); Volume 838; 89-95
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 8
    facet.materialart.
    Unknown
    Differences in the Gas and Dust Distribution in the Transitional Disk of a Sun-Like Young Star, PDS 70 (2018)
    In:  Other Sources
    Details
    Publication Date: 2019-05-30
    Description: We present ALMA 0.87 mm continuum, HCO+ J = 43 emission line, and CO J = 32 emission line data of the disk of material around the young, Sun-like star PDS 70. These data reveal the existence of a possible two-component transitional disk system with a radial dust gap of 0.42 arcsec 0.05 arcsec, an azimuthal gap in the HCO+ J = 43 moment zero map, as well as two bridge-like features in the gas data. Interestingly these features in the gas disk have no analog in the dust disk making them of particular interest. We modeled the dust disk using the Monte Carlo radiative transfer code HOCHUNK3D using a two-disk component. We nd that there is a radial gap that extends from 15 to 60 au in all grain sizes, which differs from previous work.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64788 , Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 858; 2; 112
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 9
    facet.materialart.
    Unknown
    Giant Planet Effects on Terrestrial Planet Formation and System Architecture (2019)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Using an updated collision model, we conduct a suite of high-resolution N-body integrations to probe the relationship between giant planet mass and terrestrial planet formation and system architecture. We vary the mass of the planets that reside at Jupiter's and Saturn's orbit and examine the effects on the interior terrestrial system.We find that massive giant planets are more likely to eject material from the outer edge of the terrestrial disc and produce terrestrial planets that are on smaller, more circular orbits. We do not find a strong correlation between exterior giant planet mass and the number of Earth analogues (analogous in mass and semi-major axis) produced in the system. These results allow us to make predictions on the nature of terrestrial planets orbiting distant Sun-like star systems that harbour giant planet companions on long orbits - systems that will be a priority for NASA's upcoming Wide-Field Infrared Survey Telescope (WFIRST) mission.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN69989 , Monthly Notices of the Royal Astronomical Society (ISSN 0035-8711) (e-ISSN 1365-8711); 485; 1; 541–549
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 10
    facet.materialart.
    Unknown
    A Decade of MWC 758 Disk Images: Where are the Spiral-Arm-Driving Planets? (2018)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Large-scale spiral arms have been revealed in scattered light images of a few protoplanetary disks. Theoretical models suggest that such arms may be driven by and corotate with giant planets, which has called for remarkable observational efforts to look for them. By examining the rotation of the spiral arms for the MWC 758 system over a 10 year timescale, we are able to provide dynamical constraints on the locations of their perturbers. We present reprocessed Hubble Space Telescope (HST)/NICMOS F110W observations of the target in 2005, and the new Keck/NIRC2 L'-band observations in 2017. MWC 758's two well-known spiral arms are revealed in the NICMOS archive at the earliest observational epoch. With additional Very Large Telescope (VLT)/SPHERE data, our joint analysis leads to a pattern speed of 0.6(sup +3.3, sub -0.6)/yr at 3 for the two major spiral arms. If the two arms are induced by a perturber on a near-circular orbit, its best-fit orbit is at 89 au (0."59), with a 3 lower limit of 30 au (0."20). This finding is consistent with the simulation prediction of the location of an arm-driving planet for the two major arms in the system.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64824 , The Astrophysica Journal Letters (ISSN 2041-8205) (e-ISSN 2041-8213); 857; 1; L9
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 11
    facet.materialart.
    Unknown
    Confirming Interstellar C60(+) Using the Hubble Space Telescope (2019)
    In:  Other Sources
    Details
    Publication Date: 2019-05-21
    Description: Recent advances in laboratory spectroscopy lead to the claim of ionized Buckminsterfullerene (C60(+)) as the carrier of two diffuse interstellar bands (DIBs) in the near-infrared. However, irrefutable identication of interstellar C60(+) requires a match between the wavelengths and the expected strengths of all absorption features detectable in the laboratory and in space. Here we present Hubble Space Telescope (HST) spectra of the region covering the C60(+) 9348, 9365, 9428, and 9577 absorption bands toward seven heavily reddened stars. We focus in particular on searching for the weaker laboratory C60(+) bands, the very presence of which has been a matter for recent debate. Using the novel STIS-scanning technique to obtain ultra-high signal-to-noise spectra without contamination from telluric absorption that aficted previous ground-based observations, we obtained reliable detections of the (weak) 9365, 9428 and (strong) 9577 C60(+) bands. The band wavelengths and strength ratios are sufciently similar to those determined in the latest laboratory experiments that we consider this the rst robust identication of the 9428 band, and a conclusive conrmation of interstellar C60(+).
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN68405 , Astrophysical Journal Letters (ISSN 2041-8205) (e-ISSN 2041-8213); 875; 2; L28
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 12
    facet.materialart.
    Unknown
    NuSTAR Observations of WISE J1036+0449, A Galaxy at zeta approx 1 Obscured by Hot Dust (2017)
    In:  Other Sources
    Details
    Publication Date: 2017-07-20
    Description: Hot dust-obscured galaxies (hot DOGs), selected from Wide-Field Infrared Survey Explorer's all-sky infrared survey, host some of the most powerful active galactic nuclei known and may represent an important stage in the evolution of galaxies. Most known hot DOGs are located at z 〉 1.5, due in part to a strong bias against identifying them at lower redshift related to the selection criteria. We present a new selection method that identifies 153 hot DOG candidates at z approx. 1, where they are significantly brighter and easier to study. We validate this approach by measuring a redshift z = 1.009 and finding a spectral energy distribution similar to that of higher-redshift hot DOGs for one of these objects, WISE J1036+0449 (L(sub BOL) approx. = 8 x 10(exp 46) erg/s). We find evidence of a broadened component in Mg II, which would imply a black hole mass of M(BH) approx. = 2 x 10(exp 8) Stellar Mass and an Eddington ratio of lambda(sub Edd) approx. = 2.7. WISE J1036+0449 is the first hot DOG detected by the Nuclear Spectroscopic Telescope Array, and observations show that the source is heavily obscured, with a column density of N(sub H) approx. = (2-15) x 10(exp 23)/sq cm. The source has an intrinsic 2-10 keV luminosity of approx. 6 x 10(exp 44) erg/s, a value significantly lower than that expected from the mid-infrared X-ray correlation. We also find that other hot DOGs observed by X-ray facilities show a similar deficiency of X-ray flux. We discuss the origin of the X-ray weakness and the absorption properties of hot DOGs. Hot DOGs at z 〈 or approx. 1 could be excellent laboratories to probe the characteristics of the accretion flow and of the X-ray emitting plasma at extreme values of the Eddington ratio.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN43991 , The Astrophysical Journal (ISSN ISSN 0004-637X; e-ISSN 1538-4357); Volume 835; No. 1; 105
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 13
    facet.materialart.
    Unknown
    OGLE-2016-BLG-1469L: Microlensing Binary Composed of Brown Dwarfs (2017)
    In:  Other Sources
    Details
    Publication Date: 2019-05-24
    Description: We report the discovery of a binary composed of two brown dwarfs, based on the analysis of the micro lensing event OGLE-2016-BLG-1469. Thanks to the detection of both finite-source and micro lens-parallax effects, we are able to measure both the masses M(sub 1) ~ 0.05 Solar Mass and M(sub 2) ~ 0.01 Solar Mass, and the distance D(sub L) ~ 4.5 kpc, as well as the projected separation a(sub perpendicular) ~ 0.33 au. This is the third brown-dwarf binary detected using the micro lensing method, demonstrating the usefulness of micro lensing in detecting field brown-dwarf binaries with separations of less than 1 au.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64792 , The Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 843; 1; 59
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 14
    facet.materialart.
    Unknown
    The Advanced Spectral Library (ASTRAL): Reference Spectra for Evolved M Stars (2018)
    In:  CASI
    Details
    Publication Date: 2019-05-25
    Description: The HST Treasury Program Advanced Spectral Library Project: Cool Stars was designed to collect representative, high-quality UV spectra of eight evolved FM type cool stars. The Space Telescope Imaging Spectrograph (STIS)echelle spectra of these objects enable investigations of a broad range of topics, including stellar and interstellar astrophysics. This paper provides a guide to the spectra of the two evolved M stars, the M2 Iab supergiant Oriand the M3.4 giant Cru, with comparisons to the prototypical K1.5 giant Boo. It includes identifications of the significant atomic and molecular emission and absorption features and discusses the character of the photospheric and chromospheric continua and line spectra. The fluorescent processes responsible for a large portion of the emission-line spectrum, the characteristics of the stellar winds, and the available diagnostics for hot and cool plasmas are also summarized. This analysis will facilitate the future study of the spectra, outer atmospheres, and winds, not only of these objects but of numerous other cool, low-gravity stars, for years to come.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64711 , The Astrophysicial Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 869; 2; 157
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 15
    facet.materialart.
    Unknown
    Impulsively Reflected Ions: A Plausible Mechanism for Ion Acoustic Wave Growth in Collisionless Shocks (2019)
    In:  Other Sources
    Details
    Publication Date: 2019-05-22
    Description: We present recent high time resolution observations from an oblique (43 deg) shock crossing from the Magnetospheric Multiscale mission. Short-duration bursts between 10 and 100 ms of ion acoustic waves are observed in this event alongside a persistent reflected ion population. High time resolution (150 ms) particle measurements show strongly varying ion distributions between successive measurements, implying that they are bursty and impulsive by nature. Such signatures are consistent with ion bursts that are impulsively reflected at various points within the shock. We find that, after instability analysis using a Fried-Conte dispersion solver, the insertion of dispersive ion bursts into an already stable ion distribution can lead to wave growth in the ion acoustic mode for short durations of time. We find that impulsively reflected ions are a plausible mechanism for ion acoustic wave growth in the terrestrial bow shock and, furthermore, suggest that wave growth can lead to a small but measurable momentum exchange between the solar wind ions and the reflected population.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN68433 , Journal of Geophysical Research: Space Physics (e-ISSN 2169-9402); 124; 3; 1855-1865
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 16
    facet.materialart.
    Unknown
    Correlation between SFR Surface Density and Thermal Pressure of Ionized Gas in Local Analogs of High-redshift Galaxies (2019)
    In:  Other Sources
    Details
    Publication Date: 2019-06-29
    Description: We explore the relation between the star formation rate (SFR) surface density (integration of SFR) and the interstellar gas pressure for nearby compact starburst galaxies. The sample consists of 17 green peas and 19 Lyman break analogs (LBAs). Green peas are nearby analogs of Ly alpha emitters at high redshift and LBAs are nearby analogs of Lyman break galaxies at high redshift. We measure the sizes of green peas using Hubble Space Telescope Cosmic Origins Spectrograph near-UV images with a spatial resolution of approximately 0.05 arcsec. We estimate the gas thermal pressure in H II regions by P equals N (sub total)Tk (sub B) approximately or equal to 2n (sub e)Tk (sub B). The electron density is derived using the [S II] doublet at 6716,6731 Angstroms and the temperature is calculated from the [O III] lines. The correlation is characterized by the integration of SFR equals 2.40 times 10 (sup -3) times solar mass per year per square kiloparsec times ((P divided by k (sub B)) divided by (10 ( sup 4) per cubic centimeter times K)) times (sup 1.33). Green peas and LBAs have high integration of SFR up to 1.2 solar masses per year per square kiloparsec and high thermal pressure in the H II region up to P divided by k (sub B) approximating 10 (sup 7.2) K cubic centimeters. These values are at the highest end of the range seen in nearby starburst galaxies. The high gas pressure and the correlation are in agreement with those found instar-forming galaxies at redshift approximating 2.5. These extreme pressures are shown to be responsible for driving galactic winds in nearby starbursts. These outflows may be crucial in enabling Ly alpha and Lyman-continuum to escape.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN67881 , Astrophysical Journal (ISSN 2041-8205) (e-ISSN 2041-8213); 872; 2; 146
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 17
    facet.materialart.
    Unknown
    Mutual Orbit Orientations of Transneptunian Binaries (2019)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: We present Keplerian orbit solutions for the mutual orbits of 17 transneptunian binary systems (TNBs). For ten of them, the orbit had not previously been known: 60458 2000 CM (sub 114), 119979 2002 WC (sub 19), 160091 2000 OL (sub 67), 160256 2002 PD (sub 149), 469514 2003 QA (sub 91), 469705 Kagara, 508788 2000 CQ (sub 114), 508869 2002 VT (sub 130), 1999 RT (sub 214), and 2002 XH (sub 91). Seven more are systems where the size, shape, and period of the orbit had been published, but new observations have now eliminated the sky plane mirror ambiguity in its orientation: 90482 Orcus, 120347 Salacia-Actaea, 1998 WW (sub 31), 1999 OJ (sub 4), 2000 QL (sub 251), 2001 XR (sub 254), and 2003 TJ (sub 58). The dynamical masses we obtain from TNB mutual orbits can be combined with estimates of the objects' sizes from thermal observations or stellar occultations to estimate their bulk densities. The Kagara system is currently undergoing mutual events in which one component casts its shadow upon the other and/or obstructs the view of the other. Such events provide valuable opportunities for further characterization of the system. Combining our new orbits with previously published orbits yields a sample of 35 binary orbits with known orientations that can provide important clues about the environment in which outer solar system planetesimals formed, as well as their subsequent evolutionary history. Among the relatively tight binaries, with semimajor axes less than about 5 percent of their Hill radii, prograde mutual orbits vastly outnumber retrograde orbits. This imbalance is not attributable to any known observational bias. We suggest that this distribution could be the signature of planetesimal formation through gravitational collapse of local density enhancements such as caused by the streaming instability. Wider binaries, with semimajor axes greater than 5 percent of their Hill radii, are somewhat more evenly distributed between prograde and retrograde orbits, but with mutual orbits that are aligned or anti-aligned with their heliocentric orbits. This pattern could perhaps result from Kozai-Lidov cycles coupled with tidal evolution eliminating high inclination wide binaries.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN68830 , Icarus (ISSN 0019-1035) (e-ISSN 1090-2643)
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 18
    facet.materialart.
    Unknown
    The Star-Grazing Bodies in the HD 172555 System (2018)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Kiefer et al. reported the detection of in falling Ca(sub II) absorption in HD 172555, a member of the Pictoris Moving Group (PMG). We obtained HST Space Telescope Imaging Spectrograph and Cosmic Origins Spectrograph spectroscopy of this star at 2 epochs separated by a week, and we report the discovery of infalling gas in resonant transitions of Si(sub III and IV), C(sub II and IV), and neutral atomic oxygen. Variable absorption is seen in the C(sub II) transitions and is optically thick, with covering factors which range between 58% and 68%, similar to features seen in Pictoris. The O(sub I) spectral profile resembles that of C(sub II), showing a strong low-velocity absorption to +50 km s(exp 1) in the single spectral segment obtained during orbital night, as well as what may be higher-velocity absorption. Studies of the mid-IR spectrum of this system have suggested the presence of silica. The O(sub I) absorption differs from that seen in Si(sub III), suggesting that the neutral atomic oxygen does not originate in SiO dissociation products but in a more volatile parent molecule such as CO.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64812 , The Astrophysical Journal (ISSN 0004-6256) (e-ISSN 1538-3881); 155; 6; 242
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 19
    facet.materialart.
    Unknown
    Emission-Line Metallicities from the Faint Infrared Grism Survey and VLT/MUSE (2019)
    In:  Other Sources
    Details
    Publication Date: 2019-07-02
    Description: We derive direct-measurement gas-phase metallicities of 7.4 〈 12 + log(O/H) 〈 8.4 for 14 low-mass emission- line galaxies at 0.3 〈 z 〈 0.8 identied in the Faint Infrared Grism Survey. We use deep slitless G102 grism spectroscopy of the Hubble Ultra Deep Field, dispersing light from all objects in the eld at wavelengths between 0.85 and 1.15 m. We run an automatic search routine on these spectra to robustly identify 71 emission-line sources, using archival data from Very Large Telescope (VLT)/Multi-Unit Spectroscopic Explorer (MUSE) to measure additional lines and conrm redshifts. We identify 14 objects with 0.3 〈 z 〈 0.8 with measurable [O III] 4363 emission lines in matching VLT/MUSE spectra. For these galaxies, we derive direct electron-temperature gas-phase metallicities with a range of 7.4 〈 12 + log(O/H) 〈 8.4. With matching stellar masses in the range of 10(exp 7.9) Solar Mass 〈 M(sub *) 〈 10(exp 10.4) Solar Mass, we construct a massmetallicity (MZ) relation and nd that the relation is offset to lower metallicities compared to metallicities derived from alternative methods (e.g., R(sub 23), O3N2, N2O2) and continuum selected samples. Using star formation rates derived from the H emission line, we calculate our galaxies position on the Fundamental Metallicity Relation, where we also nd an offset toward lower metallicities. This demonstrates that this emission-line-selected sample probes objects of low stellar masses but even lower metallicities than many comparable surveys. We detect a trend suggesting galaxies with higher Specic Star Formation (SSFR) are more likely to have lower metallicity. This could be due to cold accretion of metal-poor gas that drives star formation, or could be because outows of metal-rich stellar winds and SNe ejecta are more common in galaxies with higher SSFR.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN68614 , Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 874; 2; 125
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 20
    facet.materialart.
    Unknown
    High-Contrast Polarimetry Observation of the T Tau Circumstellar Environment (2018)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: We conducted high-contrast polarimetry observations of T Tau in the H-band, using the High Contrast Instrument for the Subaru Next Generation Adaptive Optics instrument mounted on the Subaru Telescope, revealing structures as near as 0farcs1 from the stars T Tau N and T Tau S. The whole T Tau system is found to be surrounded by nebula-like envelopes, and several outflow-related structures are detected in these envelopes. We analyzed the detailed polarization patterns of the circumstellar structures near each component of this triple young star system and determined constraints on the circumstellar disks and outflow structures. We suggest that the nearly face-on circumstellar disk of T Tau N is no larger than 0".8, or 117 au, in the northwest, based on the existence of a hole in this direction, and no larger than 0".27, or 40 au, in the south. A new structure, "N5," extends to about 0."42, or 59 au, southwest of the star, and is believed to be part of the disk. We suggest that T Tau S is surrounded by a highly inclined circumbinary disk with a radius of about 0."3, or 44 au, with a position angle of about 30, that is misaligned with the orbit of the T Tau S binary. After analyzing the positions and polarization vector patterns of the outflow-related structures, we suggest that T Tau S should trigger the well-known EW outflow, and is also likely to be responsible for a southwest precessing outflow "coil" and a possible south outflow.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64810 , The Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 861; 2; 133
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 21
    facet.materialart.
    Unknown
    The Chaotic Long-Term X-Ray Variability of 4U 1705-44 (2018)
    In:  CASI
    Details
    Publication Date: 2019-05-08
    Description: The low-mass X-ray binary 4U1705-44 exhibits dramatic long-term X-ray time variability with a timescale of several hundred days. The All-Sky Monitor (ASM) aboard the Rossi X-ray Timing Explorer (RXTE) and the Japanese Monitor of All-sky X-ray Image (MAXI) aboard the International Space Station together have continuously observed the source from December 1995 through May 2014. The combined ASM-MAXI data provide a continuous time series over fifty times the length of the timescale of interest. Topological analysis can help us identify fingerprints in the phase-space of a system unique to its equations of motion. The Birman- Williams theorem postulates that if such fingerprints are the same between two systems, then their equations of motion must be closely related. The phase-space embedding of the source light curve shows a strong resemblance to the double-welled nonlinear Duffing oscillator. We explore a range of parameters for which the Duffing oscillator closely mirrors the time evolution of 4U1705-44.We extract low period, unstable periodic orbits from the 4U1705-44 and Duffing time series and compare their topological information. The Duffing and 4U1705- 44 topological properties are identical, providing strong evidence that they share the same underlying template. This suggests that we can look to the Duffing equation to help guide the development of a physical model to describe the long-term X-ray variability of this and other similarly behaved X-ray binary systems.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN55635 , Monthly Notices of the Royal Astronomical Society (ISSN 0035-8711) (e-ISSN 1365-2966); 477; 4; 5220–5237
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 22
    facet.materialart.
    Unknown
    Direct Te Metallicity Calibration of R23 in Strong Line Emitters (2019)
    In:  Other Sources
    Details
    Publication Date: 2019-07-02
    Description: The gas metallicity of galaxies is often estimated using strong emission lines such as the optical lines of [O iii] and [O ii]. The most common measure is "R23," defined as ([O ii]3726, 3729 + [O iii]4959,5007)/H. Most calibrations for these strong-line metallicity indicators are for continuum selected galaxies. We report a new empirical calibration of R23 for extreme emission-line galaxies using a large sample of about 800 star-forming green pea galaxies with reliable Te -based gas-phase metallicity measurements. This sample is assembled from Sloan Digital Sky Survey (SDSS) Data Release 13 with the equivalent width of the line [O iii]5007 〉 300 or the equivalent width of the line H 〉 100 in the redshift range 0.011 〈 z 〈 0.411. For galaxies with strong emission lines and large ionization parameter (which manifests as log [O iii]4959,5007/[O ii]3726,3729 0.6), R23 monotonically increases with log(O/H) and the double-value degeneracy is broken. Our calibration provides metallicity estimates that are accurate to within ~0.14 dex in this regime. Many previous R23 calibrations are found to have bias and large scatter for extreme emission-line galaxies. We give formulae and plots to directly convert R23 and [O iii]4959,5007/[O ii]3726,3729 to log(O/H). Since green peas are best nearby analogs of high-redshift Ly emitting galaxies, the new calibration offers a good way to estimate the metallicities of both extreme emission-line galaxies and high-redshift Ly emitting galaxies. We also report on 15 galaxies with metallicities less than 1/12 solar, with the lowest metallicities being 12+log(O/H) = 7.25 and 7.26.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN67882 , Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 872; 2; 145
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 23
    facet.materialart.
    Unknown
    Observations of Fast-Moving Features in the Debris Disk of AU Mic on a Three-Year Timescale: Confirmation and New Discoveries (2018)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Context. The nearby and young M star AU Mic is surrounded by a debris disk in which we previously identified a series of large-scale arch-like structures that have never been seen before in any other debris disk and that move outward at high velocities. Aims. We initiated a monitoring program with the following objectives: (1) track the location of the structures and better constrain their projected speeds, (2) search for new features emerging closer in, and ultimately (3) understand the mechanism responsible for the motion and production of the disk features. Methods. AU Mic was observed at 11 different epochs between August 2014 and October 2017 with the IR camera and spectrograph of SPHERE. These high-contrast imaging data were processed with a variety of angular, spectral, and polarimetric differential imaging techniques to reveal the faintest structures in the disk. We measured the projected separations of the features in a systematic way for all epochs. We also applied the very same measurements to older observations from the Hubble Space Telescope (HST) with the visible cameras STIS and ACS. Results. The main outcomes of this work are (1) the recovery of the five southeastern broad arch-like structures we identified in our first study, and confirmation of their fast motion (projected speed in the range 412 km/s); (2) the confirmation that the very first structures observed in 2004 with ACS are indeed connected to those observed later with STIS and now SPHERE; (3) the discovery of two new very compact structures at the northwest side of the disk (at 0.40 and 0.55 in May 2015) that move to the southeast at low speed; and (4) the identification of a new arch-like structure that might be emerging at the southeast side at about 0.4 from the star (as of May 2016). Conclusions. Although the exquisite sensitivity of SPHERE allows one to follow the evolution not only of the projected separation, but also of the specific morphology of each individual feature, it remains difficult to distinguish between possible dynamical scenarios that may explain the observations. Understanding the exact origin of these features, the way they are generated, and their evolution over time is certainly a significant challenge in the context of planetary system formation around M stars.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64813 , The Astronomy & Astrophysics Journal (ISSN 0004-6361) (e-ISSN 1432-0746); 614; A52
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 24
    facet.materialart.
    Unknown
    Variability of Disk Emission in Pre-Main-Sequence and Related Stars. IV. Investigating the Structural Changes in the Inner Disk Region of MWC 480 (2018)
    In:  Other Sources
    Details
    Publication Date: 2019-05-24
    Description: We present five epochs of near-IR observations of the protoplanetary disk around MWC 480 (HD 31648) obtained with the SpeX spectrograph on NASAs Infrared Telescope Facility between 2007 and 2013, inclusive. Using the measured line fluxes in the Pa and Br lines, we found the mass accretion rates to be (1.262.30) x 10(exp 7) Solar Mass/yr and (1.42.01) x 10(exp 7) Solar Mass/yr, respectively, but which varied by more than 50% from epoch to epoch. The spectral energy distribution reveals a variability of about 30% between 1.5 and 10 m during this same period of time. We investigated the variability using of the continuum emission of the disk in using the Monte- Carlo Radiative Transfer Code HOCHUNK3D. We find that varying the height of the inner rim successfully produces a change in the NIR flux but lowers the far-IR emission to levels below all measured fluxes. Because the star exhibits bipolar flows, we utilized a structure that simulates an inner disk wind to model the variability in the near-IR, without producing flux levels in the far-IR that are inconsistent with existing data. For this object, variable near-IR emission due to such an outflow is more consistent with the data than changing the scale height of the inner rim of the disk.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64790 , The Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 856; 2; 103
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 25
    facet.materialart.
    Unknown
    High-Resolution, Lightweight, and Low-cost X-Ray Optics for the Lynx Observatory (2019)
    In:  CASI
    Details
    Publication Date: 2019-05-18
    Description: We describe an approach to build an x-ray mirror assembly that can meet Lynxs requirements of high-angular resolution, large effective area, light weight, short production schedule, and low-production cost. Adopting a modular hierarchy, the assembly is composed of 37,492 mirror segments, each of which measures 100 mm 100 mm 0.5 mm. These segments are integrated into 611 modules, which are individually tested and qualified to meet both science performance and spaceflight environment requirements before they in turn are integrated into 12 metashells. The 12 metashells are then integrated to form the mirror assembly. This approach combines the latest precision polishing technology and the monocrystalline silicon material to fabricate the thin and lightweight mirror segments. Because of the use of commercially available equipment and material and because of its highly modular and hierarchical building-up process, this approach is highly amenable to automation and mass production to maximize production throughput and to minimize production schedule and cost. As of fall 2018, the basic elements of this approach, including substrate fabrication, coating, alignment, and bonding, have been validated by the successful building and testing of single-pair mirror modules. In the next few years, the many steps of the approach will be refined and perfected by repeatedly building and testing mirror modules containing progressively more mirror segments to fully meet science performance, spaceflight environments, as well as programmatic requirements of the Lynx mission and other proposed missions, such as AXIS.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN68353 , Journal of Astronomical Telescopes, Instruments, and Systems; 5; 2; 021012
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 26
    facet.materialart.
    Unknown
    ALMA Reveals a Misaligned Inner Gas Disk inside the Large Cavity of a Transitional Disk (2018)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Pairs of azimuthal intensity decrements at near-symmetric locations have been seen in a number of protoplanetary disks. They are most commonly interpreted as the two shadows cast by a highly misaligned inner disk. Direct evidence of such an inner disk, however, remains largely illusive, except in rare cases. In 2012, a pair of such shadows were discovered in scattered-light observations of the near face-on disk around 2MASS J16042165- 2130284, a transitional object with a cavity 60 au in radius. The star itself is a dipper, with quasi-periodic dimming events on its light curve, commonly hypothesized as caused by extinctions by transiting dusty structures in the inner disk. Here, we report the detection of a gas disk inside the cavity using Atacama Large Millimeter/ submillimeter Array (ALMA) observations with 0".2 angular resolution. A twisted butterfly pattern is found in the moment 1 map of the CO (32) emission line toward the center, which is the key signature of a high misalignment between the inner and outer disks. In addition, the counterparts of the shadows are seen in both dust continuum emission and gas emission maps, consistent with these regions being cooler than their surroundings. Our ndings strongly support the hypothesized misaligned inner disk origin of the shadows in the J1604-2130 disk. Finally, the inclination of the inner disk would be close to 45 in contrast with 45; it is possible that its internal asymmetric structures cause the variations on the light curve of the host star.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64797 , The Astrophysical Journal (ISSN 2041-8205) (e-ISSN 2041-8213); 868; 1; L3
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 27
    facet.materialart.
    Unknown
    Orbital Characterization of GJ1108A System, and Comparison of Dynamical Mass with Model-Derived Mass for Resolved Binaries (2018)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: We report an orbital characterization of GJ1108Aab that is a low-mass binary system in the pre-main-sequence phase. Via the combination of astrometry using adaptive optics and radial velocity measurements, an eccentric orbital solution of e = 0.63 is obtained, which might be induced by the KozaiLidov mechanism with a widely separated GJ1108B system. Combined with several observed properties, we conrm that the system is indeed young. Columba is the most probable moving group, to which the GJ1108A system belongs, although its membership to the group has not been established. If the age of Columba is assumed for GJ1108A, the dynamical masses of both GJ1108Aa and GJ1108Ab (M(sub dynamical,GJ1108Aa) = 0.72 0.04 Solar Mass and M(sub dynamical,GJ1108Ab) = 0.30 0.03 Solar Mass) are more massive than what an evolutionary model predicts based on the age and luminosities. We consider that the discrepancy in mass comparison can be attributed to an age uncertainty; the system is likely older than stars in Columba, and effects that are not implemented in classical models such as accretion history and magnetic activity are not preferred to explain the mass discrepancy. We also discuss the performance of the evolutionary model by compiling similar low-mass objects in the evolutionary state based on the literature. Consequently, it is suggested that the current model on average reproduces the mass of resolved low-mass binaries without any signicant offsets.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64800 , The Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 865; 2; 152
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 28
    facet.materialart.
    Unknown
    SCExAO/CHARIS Near-Infrared Direct Imaging, Spectroscopy, and Forward-Modeling of and b: A Likely Young, Low-Gravity Superjovian Companion (2018)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: We present SCExAO/CHARIS high-contrast imaging/JHK integral eld spectroscopy of And b, a directly imaged low-mass companion orbiting a nearby B9V star. We detect And b at a high signal-to-noise ratio and extract high-precision spectrophotometry using a new forward-modeling algorithm for (A-)LOCI complementary to KLIP-FM developed by Pueyo et al. And bs spectrum best resembles that of a low-gravity L0L1 dwarf (L0L1). Its spectrum and luminosity are very well matched by 2MASS J0141-4633 and several other 12.515 M(sub J) free-oating members of the 40 Myr old TucHor Association, consistent with a system age derived from recent interferometric results for the primary, a companion mass at/near the deuterium-burning limit (13(sup +12, sub -2) M(sub J)), and a companion-to-primary mass ratio characteristic of other directly imaged planets (q 0.005(sup +0.005, sub -0.001)). We did not unambiguously identify additional, more closely orbiting companions brighter and more massive than And b down to 0".3 (15 au). SCExAO/CHARIS and complementary Keck/NIRC2 astrometric points reveal clockwise orbital motion. Modeling points toward a likely eccentric orbit: a subset of acceptable orbits include those that are aligned with the stars rotation axis. However, And bs semimajor axis is plausibly larger than 55 au and in a region where disk instability could form massive companions. Deeper high-contrast imaging of And and low-resolution spectroscopy from extreme adaptive optics systems such as SCExAO/CHARIS and higher-resolution spectroscopy from Keck/OSIRIS or, later, IRIS on the Thirty Meter Telescope could help to clarify And bs chemistry and whether its spectrum provides an insight into its formation environment.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64795 , The Astrophysical Journal (ISSN 0004-6256) (e-ISSN 1538-3881); 156; 6; 291
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 29
    facet.materialart.
    Unknown
    An Isolated Microlens Observed from K2, Spitzer, and Earth (2017)
    In:  Other Sources
    Details
    Publication Date: 2019-06-12
    Description: We present the result of microlensing event MOA-2016-BLG-290, which received observations from the two-wheel Kepler (K2), Spitzer, as well as ground-based observatories. A joint analysis of data from K2 and the ground leads to two degenerate solutions of the lens mass and distance. This degeneracy is effectively broken once the (partial) Spitzer light curve is included. Altogether, the lens is found to be an extremely low-mass star or brown dwarf (77(sup +34)(sub -23) M(sub J)) located in the Galactic bulge (6.8 0.4 kpc). MOA-2016-BLG-290 is the first microlensing event for which we have signals from three well-separated (~1 au) locations. It demonstrates the power of two-satellite microlensing experiment in reducing the ambiguity of lens properties, as pointed out independently by S. Refsdal and A. Gould several decades ago.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64721 , Astrophysical Journal Letters (ISSN 2041-8205) (e-ISSN 2041-8213); 849; 2; L31
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 30
    facet.materialart.
    Unknown
    Expected Occurrence Rates and Types of Planets Possible in the Alpha Centauri AB System (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-31
    Description: Alpha Centauri AB system contains the closest Sun-like stars to the Sun, by a large margin (factor of 2.4). Thus, they are important targets for the search of Earth-like planets. A critical question is whether such planets can exist in the system, and what their expected occurrence rate is. This paper surveys the current knowledge of occurrence rates, limits from nondetections, constraints from observations, and dynamical stability simulations, in order to answer this question.
    Keywords: Astrophysics
    Type: ARC-E-DAA-TN69636 , AbSciCon 2019; Jun 24, 2019 - Jun 28, 2019; Bellevue, WA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 31
    facet.materialart.
    Unknown
    TESS Data Release Notes: Sector 9, DR11 (2019)
    In:  CASI
    Details
    Publication Date: 2019-06-26
    Description: This release note discusses the science data products produced by the Science Processing Operations Center at Ames Research Center from Sector 9 observations made with the TESS spacecraft and cameras as a means to document instrument performance and data characteristics.
    Keywords: Astrophysics
    Type: ARC-E-DAA-TN69031
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 32
    facet.materialart.
    Unknown
    TESS Data Release Notes: Sector 10, DR14 (2019)
    In:  CASI
    Details
    Publication Date: 2019-06-26
    Description: This release note discusses the science data products produced by the Science Processing Operations Center at Ames Research Center from Sector 10 observations made with the TESS spacecraft and cameras as a means to document instrument performance and data characteristics.
    Keywords: Astrophysics
    Type: NASA/TM-2019-220220 , ARC-E-DAA-TN69634
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 33
    facet.materialart.
    Unknown
    Astro2020 Science White Paper: Prospects for Pulsar Studies at MeV Energies (2019)
    In:  CASI
    Details
    Publication Date: 2019-06-20
    Description: Enabled by the Fermi Large Area Telescope, we now know young and recycled pulsars fill the gamma-ray sky, and we are beginning to understand their emission mechanism and their distribution throughout the Galaxy. However, key questions remain: Is there a large population of pulsars near the Galactic center? Why do the most energetic pulsars shine so brightly in MeV gamma rays but not always at GeV energies? What is the source and nature of the pair plasma in pulsar magnetospheres, and what role does the polar cap accelerator play? Addressing these questions calls for a sensitive, wide-field MeV telescope, which can detect the population of MeV-peaked pulsars hinted at by Fermi and hard X-ray telescopes and characterize their spectral shape and polarization.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN69835
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 34
    facet.materialart.
    Unknown
    Faint-Source-Star Planetary Microlensing: The Discovery of the Cold Gas-Giant Planet OGLE-2014-BLG-0676Lb (2016)
    In:  CASI
    Details
    Publication Date: 2019-06-20
    Description: We report the discovery of a planet OGLE-2014-BLG-0676Lb via gravitational microlensing. Observations for the lensing event were made by the following groups: Microlensing Observations in Astrophysics; Optical Gravitational Lensing Experiment; Wise Observatory; RoboNETLas Cumbres Observatory Global Telescope; Microlensing Network for the Detection of Small Terrestrial Exoplanets; and -FUN. All analyses of the light-curve data favoura lens system comprising a planetary mass orbiting a host star. The most-favoured binary lens model has a mass ratio between the two lens masses of (4.78 +/- 0.13) 10(exp -3). Subject to some important assumptions, a Bayesian probability density analysis suggests the lens system comprises a 3.09(+1.02/-1.12) MJ planet orbiting a 0.62(+0.20/-0.22) solar mass host star at a deprojected orbital separation of 4.40(+2.16/-1.46) au. The distance to the lens system is 2.22(+0.96/-0.83) kpc. Planet OGLE-2014-BLG-0676Lb provides additional data to the growing number of cool planets discover redusing gravitational microlensing against which planetary formation theories may be tested. Most of the light in the baseline of this event is expected to come from the lens and thus high-resolution imaging observations could confirm our planetary model interpretation.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64724 , GSFC-E-DAA-TN42195 , Monthly Notices of the Royal Astronomical Society (ISSN 0035-8711 ) (e-ISSN 1365-2966); 466; 3; 2710-2717
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 35
    facet.materialart.
    Unknown
    HST/GHRS Observations of Cool, Low-Gravity Stars. VI. Mass-Loss Rates and Wind Parameters for M Giants (2018)
    In:  Other Sources
    Details
    Publication Date: 2019-06-12
    Description: The photon-scattering winds of M giants absorb parts of the chromospheric emission lines and produce self-reversed spectral features in high-resolution Hubble Space Telescope (HST)/GHRS spectra. These spectra provide an opportunity to assess fundamental parameters of the wind, including flow and turbulent velocities, the optical depth of the wind above the region of photon creation, and the stars mass-loss rate. This paper is the last paper in the series GHRS Observations of Cool, Low-Gravity Stars; the last several have compared empirical measurements of spectral emission lines with models of the winds and mass loss of K giants and supergiants. We have used the Sobolev with Exact Integration radiative transfer code, along with simple models of the outer atmosphere and wind, to determine and compare the wind characteristics of the two M-giant stars, gamma Cru (M3.5III) and mu Gem (M3IIIab), with previously derived values for low-gravity K-stars. The analysis specifies the wind parameters and calculates line profiles for the Mg II resonance lines, in addition to a range of unblended Fe II lines. Our line sample covers a large range of wind opacities and, therefore, probes a range of heights in the atmosphere. Our results show that mu Gem has a slower and more turbulent wind than gamma Cru. Also, mu Gem has a weaker chromosphere, in terms of surface flux, with respect to gamma Cru. This suggests that mu Gem is more evolved than gamma Cru. Comparing the two M giants in this work with previously studied K-giant and supergiant stars (alpha Tau, gamma Dra, and lambda Vel) reveals that the M giants have slower winds than the earlier giants, but exhibit higher mass-loss rates. Our results are interpreted in the context of the winds being driven by Alfvn waves.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN68825 , GSFC-E-DAA-TN64696 , The Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 869; 1; 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 36
    facet.materialart.
    Unknown
    A Long-Term Vision for Space-Based Interferometry (2019)
    In:  CASI
    Details
    Publication Date: 2019-08-03
    Description: The processes leading to the formation of planets; the extreme physics occurring near the event horizon of black holes; detailed studies of exoplanets through spectral-spatial mapping: new and unique insights into the physical processes involved across nearly the whole gamut of astrophysics await discovery at small angular scales. The fine spatial resolution needed to explore these processes, however, lies beyond the capabilities of current astronomical facilities and nearly all proposed future facilities. Interferometers can crack this angular resolution problem, and space-based interferometry missions promise to explore entirely new regions of scientific phase space, providing unique new insights into the physical processes lurking at small angular scales.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN70915
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 37
    facet.materialart.
    Unknown
    The Advanced Spectral Library (ASTRAL): Reference Spectra for Evolved M Stars (2018)
    In:  CASI
    Details
    Publication Date: 2019-06-11
    Description: The HST (Hubble Space Telescope) Treasury Program Advanced Spectral Library Project: Cool Stars was designed to collect representative, high-quality ultraviolet spectra of eight evolved F-M type cool stars. The Space Telescope Imaging Spectrograph (STIS) echelle spectra of these objects enable investigations of a broad range of topics, including stellar and interstellar astrophysics. This paper provides a guide to the spectra of the two evolved M stars, the M2 Iab super giant alpha Ori and the M3.4 giant gamma Cru, with comparisons to the prototypical K1.5 giant alpha Boo. It includes identifications of the significant atomic and molecular emission and absorption features and discusses the character of the photospheric and chromospheric continua and line spectra. The fluorescent processes responsible for a large portion of the emission-line spectrum, the characteristics of the stellar winds, and the available diagnostics for hot and cool plasmas are also summarized. This analysis will facilitate the future study of the spectra, outer atmospheres, and winds, not only of these objects but of numerous other cool, low-gravity stars, for years to come.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN68820 , The Astrophysical Journal (ISSN 2041-8205) (e-ISSN 2041-8213); 869; 2; 157
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 38
    facet.materialart.
    Unknown
    The HOSTS Survey-Exozodiacal Dust Measurements for 30 Stars (2018)
    In:  Other Sources
    Details
    Publication Date: 2019-06-11
    Description: The Hunt for Observable Signatures of Terrestrial Systems survey searches for dust near the habitable zones (HZs) around nearby, bright main-sequence stars. We use nulling interferometry in the N band to suppress the bright stellar light and to probe for low levels of HZ dust around the 30 stars observed so far. Our overall detection rate is 18%, including four new detections, among which are the first three around Sun-like stars and the first two around stars without any previously known circumstellar dust. The inferred occurrence rates are comparable for early-type and Sun-like stars, but decrease from 60(sup +16)(sub -21)% for stars with previously detected cold dust to 8(sup +10)(sub -3)% for stars without such excess, confirming earlier results at higher sensitivity. For completed observations on individual stars, our sensitivity is five to ten times better than previous results. Assuming a lognormal excess luminosity function, we put upper limits on the median HZ dust level of 13 zodis (95% confidence) for a sample of stars without cold dust and of 26 zodis when focusing on Sun-like stars without cold dust. However, our data suggest that a more complex luminosity function may be more appropriate. For stars without detectable Large Binocular Telescope Interferometer (LBTI) excess, our upper limits are almost reduced by a factor of two, demonstrating the strength of LBTI target vetting for future exo-Earth imaging missions. Our statistics are limited so far, and extending the survey is critical to informing the design of future exo-Earth imaging surveys.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64720 , Astronomical Journal (ISSN 0004-6256) (e-ISSN 1538-3881); 155; 5; 194
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 39
    facet.materialart.
    Unknown
    Excited Vibrational Level Rotational Constants for SiC2: A Sensitive Molecular Diagnostic for Astrophysical Conditions (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: Silacyclopropynylidene, SiC2, is a known and highly abundant circumstellar molecule. Its spectrum has been established as a major component of lines observed toward the carbon-rich star IRC +10216 (CW Leonis). It has been detected in its low-lying v(sub 3) = 1 and 2 vibrational states as well as in various isotopic compositions. Increasing sensitivity and spatial resolution will enable many more emission or absorption lines to be detected. In order to detect new molecular species, unassigned lines of known species must be identified. This work uses established ab initio quartic force fields to produce data necessary for this classification of lines related to SiC2. Agreement between the theoretical vibrational frequencies and known rotational and spectroscopic constants is quite good, as good as 5 cm(exp -1) and 3 MHz, respectively in some cases. Additionally, experimentally unknown vibrational frequencies and rotational constants are provided for the first overtones and combination bands in addition to 3(sub v3), the second overtone of the low-lying antisymmetric stretch/carbide rotation mode. Frequencies of v(sub 3) = 3 low-J rotational transitions of the main isotopic species are also estimated from published data for v(sub 3) 2. Further, we determine rotational and centrifugal distortion parameters for which in most cases vibrational effects due to the v(sub 3) mode were reduced to first, and in several cases also to second order. These values may approximate equilibrium values better than the ground state values. The data produced herein will aid in the experimental and observational characterization of this known astromolecule in order to identify some of the unassigned lines for a known entity.
    Keywords: Astrophysics
    Type: ARC-E-DAA-TN28176
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 40
    facet.materialart.
    Unknown
    Resolving Faint Structures in the Debris Disk Around TWA 7* Tentative Detections of an Outer Belt, a Spiral Arm, and a Dusty Cloud (2018)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Context. Debris disks are the intrinsic by-products of the star and planet formation processes. Most likely due to instrumental limitations and their natural faintness, little is known about debris disks around low mass stars, especially when it comes to spatially resolved observations. Aims. We present new VLT/SPHERE IRDIS dual-polarization imaging (DPI) observations in which we detect the dust ring around the M2 spectral type star TWA 7. Combined with additional angular differential imaging observations we aim at a fine characterization of the debris disk and setting constraints on the presence of low-mass planets. Methods. We modeled the SPHERE DPI observations and constrain the location of the small dust grains, as well as the spectral energy distribution of the debris disk, using the results inferred from the observations, and performed simple N-body simulations. Results. We find that the dust density distribution peaks at ~0.72 (25 au), with a very shallow outer power-law slope, and that the disk has an inclination of ~13 with a position angle of ~91 east of north. We also report low signal-to-noise ratio detections of an outer belt at a distance of ~1.5 (~52 au) from the star, of a spiral arm in the southern side of the star, and of a possible dusty clump at 0.11. These findings seem to persist over timescales of at least a year. Using the intensity images, we do not detect any planets in the close vicinity of the star, but the sensitivity reaches Jovian planet mass upper limits. We find that the SED is best reproduced with an inner disk at ~0.2 (~7 au) and another belt at 0.72 (25 au). Conclusions. We report the detections of several unexpected features in the disk around TWA 7. A yet undetected 100 Solar Mass planet with a semi-major axis at 2030 au could possibly explain the outer belt as well as the spiral arm. We conclude that stellar winds are unlikely to be responsible for the spiral arm.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64806 , Astronomy & Astrophysics (ISSN 0004-6361) (e-ISSN 1432-0746); 617; A109
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 41
    facet.materialart.
    Unknown
    Subaru/HiCIAO HK(sub S) Imaging of LKHa 330: Multi-Band Detection of the Gap and Spiral-Like Structures (2018)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: We present H- and K s-bands observations of the LkH 330 disk with a multi-band detection of the large gap and spiral-like structures. The morphology of the outer disk (r ~ 0."3) at PA = 045 and PA = 180290 is likely density wave-induced spirals, and comparison between our observational results and simulations suggests a planet formation. We have also investigated the azimuthal profiles at the ring and the outer-disk regions as well as radial profiles in the directions of the spiral-like structures and semimajor axis. Azimuthal analysis shows a large variety in wavelength and implies that the disk has non-axisymmetric dust distributions. The radial profiles in the major-axis direction (PA = 271) suggest that the outer region (r 0."25) may be influenced by shadows of the inner region of the disk. The spiral-like directions (PA = 10 and 230) show different radial profiles, which suggests that the surfaces of the spiral-like structures are highly flared and/or have different dust properties. Finally, a color map of the disk shows a lack of an outer eastern region in the H-band disk, which may hint at the presence of an inner object that casts a directional shadow onto the disk.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64807 , The Astrophysical Journal (ISSN 0004-6256) (e-ISSN 1538-3881); 156; 2; 63
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 42
    facet.materialart.
    Unknown
    SCExAO/CHARIS Near-IR High-Contrast Imaging and Integral Field Spectroscopy of the HIP 79977 Debris Disk (2018)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: We present new, near-infrared (1.12.4 m) high-contrast imaging of the bright debris disk surrounding HIP 79977 with the Subaru Coronagraphic Extreme Adaptive Optics system (SCExAO) coupled with the CHARIS integral eld spectrograph. SCExAO/CHARIS resolves the disk down to smaller angular separations of (0".11; r 14 au) and at a higher signicance than previously achieved at the same wavelengths. The disk exhibits a marginally signicant eastwest brightness asymmetry in H band that requires conrmation. Geometrical modeling suggests a nearly edge-on disk viewed at a position angle of 114.6 east of north. The disk is best-t by scattered-light models assuming strongly forward-scattering grains (g 0.50.65) conned to a torus with a peak density at r0 5375 au. We nd that a shallow outer density power law of (sub out) = 1 to 3 and are index of = 1 are preferred. Other disk parameters (e.g., inner density power law and vertical scale height) are more poorly constrained. The disk has a slightly blue intrinsic color and its prole is broadly consistent with predictions from birth ring models applied to other debris disks. While HIP 79977s disk appears to be more strongly forward- scattering than most resolved disks surrounding 530 Myr old stars, this difference may be due to observational biases favoring forward-scattering models for inclined disks versus lower inclination, ostensibly neutral-scattering disks like HR 4796As. Deeper, higher signal-to-noise SCExAO/CHARIS data can better constrain the disks dust composition.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64796 , The Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 156; 6; 279
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 43
    facet.materialart.
    Unknown
    Studies of the Coldest Brown Dwarfs with the James Webb Space Telescope (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: The coolest T and Y-class Brown Dwarf objects are very faint and are therefore very poorly understood, since they are barely detectable with the current astronomical instrumentation. The upcoming James Webb Space Telescope now in development for a launch in the Fall of 2018 will have vastly increased sensitivity in the near and mid-infrared compared to any current facilities and will not be affected by telluric absorption over its entire wavelength range of operations. As a result it will be an ideal tool to obtain information about the composition and temperature-pressure structure in these objects' atmospheres. This presentation will outline the JWST guaranteed time observing plans for these studies.
    Keywords: Astrophysics
    Type: ARC-E-DAA-TN30813 , Cool Stars 19; Jun 06, 2016 - Jun 10, 2016; Uppsala; Sweden
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 44
    facet.materialart.
    Unknown
    The Foreign Clast Populations of Anomalous Polymict Urelite Almahata Sitta (Asteroid 2008 TC(sub3) and Typical Polymict Ureilites: Implications for Asteroid-Meteorite Connections (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: Almahata Sitta (AhS) is the first meteorite to originate from an asteroid (2008 TC3) that had been studied in space before it hit Earth [1,2]. It is also unique because the fallen fragments comprise a variety of types: approximately 69% ureilites (achondrites) and 31% chondrites [3]. Two models have been proposed for the origin 2008 TC3: 1) an accretionary model [3,4]; or 2) a regolith model [5,6]. Typical polymict ureilites are interpreted to represent regolith, and contain a few % foreign clasts [7,8]. The most common are dark (CC matrix-like) clasts similar to those in many meteoritic breccias [9]. A variety of other chondrites, as well as achondrites (angrites), have also been reported [7,9,10]. We have been working to determine the full diversity of these clasts [10-13] for comparison with AhS. We discuss implications for mixing of materials in the early solar system and the origin of 2008 TC3.
    Keywords: Astrophysics
    Type: JSC-CN-35762 , Asteroid-Meteorite Connections Workshop; Apr 21, 2016 - Apr 22, 2016; Los Angeles,CA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 45
    facet.materialart.
    Unknown
    The Cosmic Microwave Background: Detection and Interpretation of the First Light (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: A host of astrophysical observations suggest the early Universe was incredibly hot, dense, and homogeneous. A powerful and useful probe of this epoch is provided by the relic radiation, which we refer to today as the Cosmic Microwave Background (CMB). Precision maps of this light contain the earliest glimpse of the Universe after the Big Bang and signatures of the evolution of its contents. By exploiting these clues, constraints on the age, mass density, detailed composition, and geometry of the Universe can be made. A brief survey of the evolution of the radiometric and polarimetric imaging systems used in advancing our understanding of the early Universe will be reviewed. A survey of detector technologies, instrumentation techniques, and experimental challenges encountered in these efforts will be presented.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN29879 , Colloquium; Feb 26, 2016; Villanova, PA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 46
    facet.materialart.
    Unknown
    Stellar Origins of C-13 and N-15-Enriched Presolar SiC Grains (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: Extreme excesses of 13 C ( C (12 C/ 13 C〈10) and 15 N ( N (14 N/ 15 N〈 20) in rare presolar SiC 20) in rare presolar SiClar SiC grains have been considered diagnostic of an origin in classical novae [1], though an origin in core-collapse supernovae (CCSNe) has also been proposed [2]. We report multi-element isotopic data for 19 13 C- and 15 N-enriched presolar SiC grains(12 C/13 C〈16 and 14 N/ 15 N〈~150) from an acid resistant residue of the Murchison meteorite. These grains are enriched in 13 C and15 N, but with quite diverse Si isotopic signatures. Four grains with isotopic signatures. Four grains with isotopic signatures. Four grains with isotopic signatures. Four grains with isotopic signatures.
    Keywords: Astrophysics
    Type: JSC-CN-35396 , International Conference on Nuclei in the Cosmos (NIC-XIV 2016); Jun 19, 2016 - Jun 24, 2016; Niigata; Japan
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 47
    facet.materialart.
    Unknown
    Identification of Highly Fractionated (18)O-Rich Silicate Grains in the Queen Alexandra Range 99177 CR3 Chondrite (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: Carbonaceous chondrites contain a mixture of solar system condensates, presolar grains, and primitive organic matter. The CR3 chondrite QUE 99177 has undergone minimal al-teration [1], exemplified by abundant presolar silicates [2, 3] and anomalous organic matter [4]. Oxygen isotopic imaging studies of this meteorite have focused on finding submicrometer anomalous grains in fine-grained regions of thin sections. Here we present re-sults of an O isotopic survey of larger matrix grains.
    Keywords: Astrophysics
    Type: JSC-CN-33568 , Annual Meeting of the Meteoritical Society; Jul 27, 2015 - Jul 31, 2015; Berkeley, CA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 48
    facet.materialart.
    Unknown
    Taxonomies and Albedos of Near-Earth Asteroids (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: Characterizing near-Earth asteroids (NEAs) can help to assess the risk of possible impactors. Over many decades, asteroids have been spectrally classified into numerous taxonomic systems, most notably those of Tholen, Bus, and Bus-DeMeo. By mapping these various taxonomic systems to broader categories called complexes, it is easier to study the relationship between classifications and other physical parameters. There has recently been an increase in the number of objects with measured albedos which is advantageous for characterization because the albedo and absolute magnitude can be used to determine diameter. Knowing an asteroids diameter helps us better understand dangers they may pose.
    Keywords: Astrophysics
    Type: ARC-E-DAA-TN34991
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 49
    facet.materialart.
    Unknown
    Lynx: Simply Designed for Maximum Science Return (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: No abstract available
    Keywords: Astrophysics
    Type: MSFC-E-DAA-TN64281 , Meeting of the American Astronomical Society; Jan 06, 2019 - Jan 10, 2019; Seattle, WA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 50
    facet.materialart.
    Unknown
    Searching for the Origin of the High-Energy Emission from GRB 170817A (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: No abstract available
    Keywords: Astrophysics
    Type: MSFC-E-DAA-TN64478 , American Astornomical Society (AAS) Meeting; Jan 06, 2019 - Jan 10, 2019; Seattle, WA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 51
    facet.materialart.
    Unknown
    STROBE-X: X-ray Timing & Spectroscopy on Dynamical Timescales from Milliseconds to Years (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: We describe a probe-class mission concept that provides an unprecedented view of the X-ray sky, performing timing and 0.2-30 keV spectroscopy over timescales from microseconds to years. The Spectroscopic Time-Resolving Observatory for Broadband Energy X-rays (STROBE-X) has three key science drivers: (1) measuring the spin distribution of accreting black holes, (2) understanding the equation of state of dense matter, and (3) exploring the properties of the precursors and electromagnetic counterparts of gravitational wave sources. To perform these science investigations, STROBE-X comprises three primary instruments. The first uses an array of lightweight optics (3-m focal length) that concentrate incident photons onto solid state detectors with CCD-level (85-130 eV) energy resolution, 100 ns time resolution, and low background rates to cover the 0.2-12 keV band. This technology is scaled up from NICER, with enhanced optics to take advantage of the longer focal length of STROBE-X. The second uses large-area collimated silicon drift detectors, developed for ESA's LOFT, to cover the 2-30 keV band. These two instruments each provide an order of magnitude improvement in effective area compared with its predecessor (NICER and RXTE, respectively). Finally, a sensitive sky monitor triggers pointed observations, provides high duty cycle, high time resolution, high spectral resolution monitoring of the X-ray sky with ~20 times the sensitivity of the RXTE ASM, and enables multi-wavelength and multi-messenger studies on a continuous, rather than scanning basis. The STROBE-X mission concept is a rapidly repointable observatory in low-Earth orbit, similar to RXTE or Swift, and will be presented to the 2020 Astrophysics Decadal Survey for consideration as a probe-class mission.
    Keywords: Astrophysics
    Type: MSFC-E-DAA-TN64215 , Meeting of the American Astronomical Society (AAS); Jan 06, 2019 - Jan 10, 2019; Seattle,WA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 52
    facet.materialart.
    Unknown
    Energetic Particles of Cosmic Accelerators I: Galactic Accelerators (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: The high-energy universe has revealed that energetic particles are ubiquitous in the cosmos and play a vital role in the cultivation of cosmic environments on all scales. Our pursuit of more than a century to uncover the origins and fate of these cosmic energetic particles has given rise to some of the most interesting and challenging questions in astrophysics. Energetic particles in our own galaxy, galactic cosmic rays (GCRs), engage in a complex interplay with the interstellar medium and magnetic fields in the galaxy, giving rise to many of its key characteristics. For instance, GCRs act in concert with galactic magnetic fields to support its disk against its own weight. GCR ionization and heating are essential ingredients in promoting and regulating the formation of stars and protostellar disks. GCR ionization also drives astrochemistry, leading to the build up of complex molecules in the interstellar medium. GCR transport throughout the galaxy generates and maintains turbulence in the interstellar medium, alters its multi-phase structure, and amplifies magnetic fields. GCRs could even launch galactic winds that enrich the circumgalactic medium and alter the structure and evolution of galactic disks. As crucial as they are for many of the varied phenomena in our galaxy, there is still much we do not understand about GCRs. While they have been linked to supernova remnants (SNRs), it remains unclear whether these objects can fully account for their entire population, particularly at the lower (approximately less than 1 GeV per nucleon) and higher (~PeV) ends of the spectrum. In fact, it is entirely possible that the SNRs that have been found to accelerate CRs merely re-accelerate them, leaving the origins of the original GCRs a mystery. The conditions for particle acceleration that make SNRs compelling source candidates are also likely to be present in sources such as protostellar jets, superbubbles, and colliding wind binaries (CWBs), but we have yet to ascertain their roles in producing GCRs. For that matter, key details of diffusive shock acceleration (DSA) have yet to be revealed, and it remains to be seen whether DSA can adequately explain particle acceleration in the cosmos. This White Paper is the first of a two-part series highlighting the most well-known high-energy cosmic accelerators and contributions that MeV gamma-ray astronomy will bring to understanding their energetic particle phenomena. For the case of GCRs, MeV astronomy will: 1) Search for fresh acceleration of GCRs in SNRs; 2) Test the DSA process, particularly in SNRs and CWBs; 3) Search for signs of CR acceleration in protostellar jets and superbubbles.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN66970
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 53
    facet.materialart.
    Unknown
    Sugar Derivatives in Residues Produced from the UV Irradiation of Astrophysical Ice Analogs (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: A large variety of organic compounds of astrobiological and prebiotic interest have been detected in carbonaceous meteorites. These include amino acids, carboxylic acids, amphiphiles, functionalized nitrogen heterocycles such as nucleobases, functionalized polycylic aromatic hydrocarbons such as quinones, and sugar derivatives. The sugar derivatives identified in the Murchison and Murray meteorites are mainly sugar alcohols and sugar acids, and only the smallest sugar (dihydroxyacetone) has been detected. The presence of such a variety of organics in meteorites strongly suggests that molecules essential to life can form abiotically under astrophysical conditions. This hypothesis is further supported by laboratory studies in which astrophysical ice analogs (mixtures of H2O, CO, CO2, CH3OH, CH4, NH3, etc.) are subjected to ultraviolet (UV) irradiation at low temperature (〈15 K) to simulate cold interstellar environments. These studies show that the organic residues recovered at room temperature after irradiation contain amino acids, amphiphiles, nucleobases, sugar derivatives, as well as other complex organic compounds. The finding of such compounds under plausible interstellar conditions is consistent with the presence of organic compounds in meteorites. Until very recently, no systematic search for the presence of sugar derivatives in laboratory residues had been carried out. The detection of ribose, the sugar constituent of RNA in all living systems, as well as other sugars, sugar alcohols, and sugar acids have been recently reported in one organic residue produced from the UV irradiation of an H2O:CH3OH:NH3 (10:3.5:1) ice mixture at 80 K. In this work, we present a detailed study of organic residues produced from the UV irradiation ice mixtures of several starting compositions (containing H2O, CH3OH, CO, CO2, and/or NH3) at 〈15 K for their sugar derivative content. Our results confirm the presence of all 3C5C sugar alcohols, several 3C5C sugars, and all 3C4C sugar acids (in decreasing order of abundances) in the residues. The higher abundances of sugar alcohols in these residues suggest a pathway in which sugar alcohols are formed first, while the formation of sugars and sugar acids require more steps. Finally, our results are compared with the detection of sugars derivatives in primitive meteorites.
    Keywords: Astrophysics
    Type: ARC-E-DAA-TN37318 , 253rd ACS National Meeting and Exposition; Apr 02, 2017 - Apr 06, 2017; San Francisco, CA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 54
    facet.materialart.
    Unknown
    Time Series Analysis in the Search for Other Worlds Through Transit Photometry (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: The Kepler Mission launched in June 2009 to commence NASA's first mission to search for potentially habitable, Earth-size planets orbiting Sun-like stars. Kepler discovered explanets via the transit method: searching for minute (100 ppm) drops in brightness lasting 1 - 13 hours corresponding to occasions where the planet crosses the face of its host star from Kepler's point of view. The exquisite precision required to carry out the Kepler mission (20 ppm in 6.5 hours) pushed astronomical time series analysis to the limits, and motivated the development of novel algorithmic approaches. Transit signatures of rocky planets are often dwarfed by the intrinsic stellar variability, which is not white noise, and often is non-stationary, and by instrumental systematic effects, which can include transients and electronic artifacts. Surmounting this challenging regime of weak, temporally compact, periodic signals in observation noise with strong systematics and other sources of variability motivated the development of 1) an overcomplete, non-decimated, wavelet-based matched filter to jointly estimate the properties of the non-stationary, non-white observation noise process, and 2) a multi-scale, maximum a posteriori (msMAP) approach to identifying and removing instrumental systematic effects. After over nine years of observations, the Kepler spacecraft finally ran out of fuel in November 2018, ending its data collection activities. Over 2300 planets were discovered by Kepler in its primary mission, and over 355 have been discovered by K2, the repurposed mission that followed Kepler's primary mission after the loss of a second reaction wheel in May 2013. We have ported the Kepler science pipeline for the Transiting Exoplanet Survey Satellite (TESS) Mission, which began science observations in July 2019, and report initial results and performance of the modified science pipeline.The Kepler and TESS Missions are supported by NASA's Science Mission Directorate.
    Keywords: Astrophysics
    Type: ARC-E-DAA-TN63583 , Astronomical Time Series 2019 (NCTS 37182-19); Jan 21, 2019 - Jan 24, 2019; Heidelberg; Germany
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 55
    facet.materialart.
    Unknown
    Design, Implementation, and Performance of the Astro-H Soft X-Ray Spectrometer Aperture Assembly and Blocking Filters (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: The calorimeter array of the JAXA Astro-H (renamed Hitomi) soft x-ray spectrometer (SXS) was designed to provide unprecedented spectral resolution of spatially extended cosmic x-ray sources and of all cosmic x-ray sources in the Fe-K band around 6 keV. The properties that made the SXS array a powerful x-ray spectrometer also made it sensitive to photons from the entire electromagnetic band as well as particles. If characterized as a bolometer, it would have had a noise equivalent power of 〈4 10(exp 18) W/((Hz)(exp 0.5)). Thus, it was imperative to shield the detector from thermal radiation from the instrument and optical and UV photons from the sky. In addition, it was necessary to shield the coldest stages of the instrument from the thermal radiation emanating from the warmer stages. These needs were addressed by a series of five thin-film radiation-blocking filters, anchored to the nested temperature stages, that blocked long-wavelength radiation while minimizing x-ray attenuation. The aperture assembly was a system of barriers, baffles, filter carriers, and filter mounts that supported the filters and inhibited their potential contamination. The three outer filters also had been equipped with thermometers and heaters for decontamination. We present the requirements, design, implementation, and performance of the SXS aperture assembly and blocking filters.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN66167 , Journal Astronomical Telescopes, Instruments, and Systems; 4; 1; 011215
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 56
    facet.materialart.
    Unknown
    Astronomical X-Ray Optics Using Mono-Crystalline Silicon: High Resolution, Light Weight, and Low Cost (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: X-ray astronomy critically depends on X-ray optics. The capability of an X-ray telescope is largelydetermined by the point-spread function (PSF) and the photon-collection area of its mirrors, the same astelescopes in other wavelength bands. Since an X-ray telescope must be operated above the atmosphere inspace and that X-rays reflect only at grazing incidence, X-ray mirrors must be both lightweight and thin, bothof which add significant technical and engineering challenge to making an X-ray telescope. In this paper wereport our effort at NASA Goddard Space Flight Center (GSFC) of developing an approach to making an Xraymirror assembly that can be significantly better than the mirror assembly currently flying on the ChandraX-ray Observatory in each of the three aspects: PSF, effective area per unit mass, and production cost per uniteffective area. Our approach is based on the precision polishing of mono-crystalline silicon to fabricate thinand lightweight X-ray mirrors of the highest figure quality and micro-roughness, therefore, having thepotential of achieving diffraction-limited X-ray optics. When successfully developed, this approach will makeimplementable in the 2020s and 2030s many X-ray astronomical missions that are currently on the drawingboard, including sounding rocket flights such as OGRE, Explorer class missions such as STAR-X andFORCE, Probe class missions such as AXIS, TAP, and HEX-P, as well as large missions such as Lynx.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN66158 , Space Telescopes and Instrumentation 2018: Ultraviolet to Gamma Ray; 10699; 106990O|SPIE Astronomical Telescopes + Instrumentation, 2018,; Jun 10, 2018 - Jun 15, 2018; Austin, TX; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 57
    facet.materialart.
    Unknown
    Ray-Tracing Simulation and In-Orbit Performance of the ASTRO-H Hard X-Ray Telescope (HXT) (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: A ray-trace simulation code for the Hard X-ray Telescope (HXT) on board the Hitomi (ASTRO-H) satellite is beingdeveloped. The half power diameter and effective area simulated based on the code are consistent with groundmeasurements within 10%. The HXT observed the pulsar wind nebula G21.5-0.9 for 105 ksec. We confirmed that theencircled energy function and the half power diameter obtained from the data are consistent with the ground measurements.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN64667 , SPIE ASTRONOMICAL TELESCOPES + INSTRUMENTATION; Jun 26, 2016 - Jul 01, 2016; Edinburgh; United Kingdom|Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray; 9905; 990541
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 58
    facet.materialart.
    Unknown
    The Physics of Accretion Onto Highly Magnetized Neutron Stars (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: Studying the physical processes occurring in the region just above the magnetic polesof strongly magnetized, accreting binary neutron stars is essential to our understanding of stellarand binary system evolution. Perhaps more importantly, it provides us with a natural laboratoryfor studying the physics of high temperature and density plasmas exposed to extreme radiation,gravitational, and magnetic fields. Observations over the past decade have shed new light on themanner in which plasma falling at near the speed of light onto a neutron star surface is halted. Recentadvances in modeling these processes have resulted in direct measurement of the magnetic fieldsand plasma properties. On the other hand, numerous physical processes have been identified thatchallenge our current picture of how the accretion process onto neutron stars works. Observationand theory are our essential tools in this regime because the extreme conditions cannot be duplicatedon Earth. This white paper gives an overview of the current theory, the outstanding theoreticaland observational challenges, and the importance of addressing them in contemporary astrophysicsresearch.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN66958
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 59
    facet.materialart.
    Unknown
    Gravitational-Wave Astronomy in the 2020s and Beyond: A View Across the Gravitational Wave Spectrum (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: One of the most notable developments since the 2010 Decadal Survey is the addition of gravitationalwaves (GW) to the astronomers' suite of tools for understanding the Universe. LIGO's2015 detection of gravitational waves (Abbott et al. 2016) from the merger of a pair of black holesroughly 30 times the mass of our Sun garnered tremendous excitement from both the public andthe scientific community and raised interesting questions as to the origin of such systems. To datea total of 11 confirmed detections have been announced, including the first GW signals from themerger of neutron stars in 2017 seen by LIGO and Virgo (Abbott et al. 2017). That event wasassociated with a gamma ray burst; the subsequent kilonovae and afterglow was perhaps the mostthoroughly-observed astronomical event of all time (Abbott et al. 2017b). In the coming decades,with continued investment, the ground-based network will continue to improve in both the numberand sensitivity of detectors at high frequencies, pulsar timing arrays such as NANOGrav willuncover stochastic sources of gravitational waves and then single sources at low frequencies, andLISA will begin to probe the mid-frequency band from space. In this white paper, we presenta broad outline of the scientific impact of these facilities in the coming decade and the 2030s,emphasizing the ways in which
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN66963
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 60
    facet.materialart.
    Unknown
    Asteroid Characterization Priorities for Planetary Defense (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: We propose a prioritized list of asteroid characterization needs for planetary defense. In particular, we consider the properties of asteroids that are of greatest interest for assessment of planetary defense options, including gravity tractors, kinetic impactors, and nuclear explosives. In addition, much of our discussion is relevant for impact assessments and subsequent emergency-response planning. Rather than intending this as a definitive answer, however, our purpose is to stimulate and focus disscussion regarding characterization needs for planetary defense, with a specific list as a starting point. A key theme is understanding the sensitivity of the outcome of an asteroid deflection or disruption effort to the asteroids physical properties.There is a range of previous work relevant to our topic, including some explicit discussions as well as many more that are implicitly relevant. We incorporate elements from such reports while extending them using our own experience and perspectives. After introducing our prioritized list, we provide further discussion on each element, with details on the relevance of each characteristic for modeling purposes, our rationale for the assigned priority, and examples of analyses that require improved characterization information. Our goal is to establish a framework that can be modified and adapted by the community for a variety of purposes, such as mission design and optimization, development of new measurement techniques, or prioritization of research efforts. The objective is to increase understanding and reduce uncertainties in the specific aspects of characterization that most benefit accurate assessments of practical techniques for planetary defense.
    Keywords: Astrophysics
    Type: ARC-E-DAA-TN21736 , IAA Planetary Defense Conference; Apr 13, 2015 - Apr 17, 2015; Frascati; Italy
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 61
    facet.materialart.
    Unknown
    Laboratory Studies of Cosmic Dust with NASA Ames' COSmIC Facility Applications to Interstellar and Planetary Issues (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: I will present and discuss the unique characteristics and capabilities of the laboratory facility, COSmIC, that was developed at NASA Ames to generate, process and analyze interstellar, circumstellar and planetary analogs in the laboratory. COSmIC stands for Cosmic Simulation Chamber and is dedicated to the study of molecules and ions under the low temperature and high vacuum conditions that are required to simulate interstellar, circumstellar and planetary physical environments in space. COSmIC integrates a variety of state-of-the-art instruments that allow forming, processing and monitoring simulated space conditions for planetary, circumstellar and interstellar materials in the laboratory. COSmIC is composed of a Pulsed Discharge Nozzle (PDN) expansion that generates a free jet supersonic expansion coupled to two ultrahigh-sensitivity, complementary in situ diagnostics: a Cavity Ring Down Spectroscopy (CRDS) system for photonic detection and a Reflectron Time-Of-Flight Mass Spectrometer (ReTOF-MS) for mass detection. Recent, unique, laboratory astrophysics results that were obtained using the capabilities of COSmIC will be discussed, in particular the progress that have been achieved in deciphering the diffuse interstellar bands (DIBs) and in monitoring in the laboratory the formation of solid dust grains from their gas-phase molecular precursors in environments as varied as stellarcircumstellar outflow and planetary atmospheres. Plans for future, next generation, laboratory experiments on cosmic molecules and grains in the growing field of laboratory astrophysics will also be addressed as well as the implications of these studies for current and upcoming space missions.
    Keywords: Astrophysics
    Type: ARC-E-DAA-TN20172 , IRAP; Feb 10, 2015; Toulouse; France
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 62
    facet.materialart.
    Unknown
    MoonBEAM: A Beyond Earth-Orbit Gamma-Ray Burst Detector for Multi-Messenger Astronomy (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: Moon Burst Energetics All-sky Monitor (MoonBEAM) is a CubeSat concept of deploying gamma-ray detectors in cislunar space to increase gamma-ray burst detections and improve localization precision with the timing triangulation technique. A gamma-ray instrument in cislunar orbit will have greatly reduced sky blockage compared to instruments in low Earth orbit. Working in conjunction with another instrument in low Earth orbit, MoonBEAM can also help constrain the arrival direction of the wavefront to an annulus on the sky by utilizing the light arrival times between the different orbits. This method has been demonstrated by the Interplanetary Gamma- Ray Burst Timing Network. However, delays in data downlink for instruments outside the Tracking and Data Relay Satellite network prevent rapid follow-up observations. We present here a gamma-ray CubeSat concept in Earth-Moon L3 halo orbit that is capable of faster response and provide a timing baseline for localization improvement. Such an instrument would aid in the gravitational wave follow-up observations in other wavelengths to identify the gamma-ray burst afterglow and kilonova emission. Reducing the region of interest makes identifying afterglows much faster, allowing for rapid on-source observations and monitoring of the rise and decay times. It will also prevent source confusion between two transients and enable robust association. A gamma-ray detection could also increase the confidence of a simultaneous but marginal gravitational wave signal, extending the detection horizon. MoonBEAM is a 12U CubeSat concept of deploying gamma-ray detectors in cislunar space to increase gamma-ray burst detections and improve localization precision with the timing triangulation technique. Such an instrument would probe the extreme processes in cosmic collision of compact objects and facilitate multi-messenger time-domain astronomy to explore the end of stellar life cycles and black hole formations.
    Keywords: Astrophysics
    Type: MSFC-E-DAA-TN60786 , International Fermi Symposium; Oct 14, 2018 - Oct 19, 2018; Baltimore, MD; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 63
    facet.materialart.
    Unknown
    Mapping High-Velocity H-alpha and Lyman-alpha Emission from Supernova 1987A (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: We present new Hubble Space Telescope images of high-velocity H-alpha and Lyman-alpha emission in the outer debris of SN 1987A. The H-alpha images are dominated by emission from hydrogen atoms crossing the reverse shock. For the first time we observe emission from the reverse shock surface well above and below the equatorial ring, suggesting a bipolar or conical structure perpendicular to the ring plane. Using the H-alpha imaging, we measure the mass flux of hydrogen atoms crossing the reverse shock front, in the velocity intervals (7,500 〈 V(sub obs) 〈 2,800 km/s) and (1,000 〈 V(sub obs) 〈 7,500 km/s), M(sub H) = 1.2 10(exp 3) M/ y. We also present the first Lyman-alpha imaging of the whole remnant and new Chandra X-ray observations. Comparing the spatial distribution of the Lyman-alpha and X-ray emission, we observe that the majority of the high-velocity Lyman-alpha emission originates interior to the equatorial ring. The observed Lyman-alpha/H-alpha photon ratio, R(L-alpha/H-alpha) approx. = 17, is significantly higher than the theoretically predicted ratio of approx. = 5 for neutral atoms crossing the reverse shock front. We attribute this excess to Lyman-alpha emission produced by X-ray heating of the outer debris. The spatial orientation of the Lyman-alpha and X-ray emission suggests that X-ray heating of the outer debris is the dominant Lyman-alpha production mechanism in SN 1987A at this phase in its evolution.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN20964 , The Astrophysical Journal Letters (ISSN 2041-8213); 801; 1; L16
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 64
    facet.materialart.
    Unknown
    Unveiling the Secrets of Metallicity and Massive Star Formation Using DLAs Along Gamma-Ray Bursts (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: We present the largest, publicly available, sample of Damped Lyman-alpha systems (DLAs) along Swift discovered Gamma-ray Bursts (GRB) line of sights in order to investigate the environmental properties of long GRB hosts in the z = 1.8 6 redshift range. Compared with the most recent quasar DLAs sample (QSO-DLA), our analysis shows that GRB-DLAs probe a more metal enriched environment at z approximately greater than 3, up to [X/H] approximately 0.5. In the z = 2 3 redshift range, despite the large number of lower limits, there are hints that the two populations may be more similar (only at 90% significance level) than at higher redshifts. Also, at high-z, the GRB-DLA average metallicity seems to decline at a shallower rate than the QSO-DLAs: GRB-DLA hosts may be polluted with metals at least as far as approximately 2 kpc from the GRB explosion site, probably due to previous star-formation episodes and/or supernovae explosions. This shallow metallicity trend, extended now up to z approximately 5, confirms previous results that GRB hosts are star-forming and have, on average, higher metallicity than the general QSO-DLA population. Finally, our host metallicity measurements are broadly consistent with the predictions derived from the hypothesis of two channels of GRB progenitors, one of which is mildly affected by a metallicity bias, although more data are needed to constrain the models at z approximately greater than 4.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN21332 , The Astrophysical Journal (e-ISSN 2041-8213); 804; 1; 51
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 65
    facet.materialart.
    Unknown
    Destruction of Interstellar Dust in Evolving Supernova Remnant Shock Waves (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Supernova generated shock waves are responsible for most of the destruction of dust grains in the interstellar medium (ISM). Calculations of the dust destruction timescale have so far been carried out using plane parallel steady shocks, however that approximation breaks down when the destruction timescale becomes longer than that for the evolution of the supernova remnant (SNR) shock. In this paper we present new calculations of grain destruction in evolving, radiative SNRs. To facilitate comparison with the previous study by Jones et al. (1996), we adopt the same dust properties as in that paper. We find that the efficiencies of grain destruction are most divergent from those for a steady shock when the thermal history of a shocked gas parcel in the SNR differs significantly from that behind a steady shock. This occurs in shocks with velocities 200 km s(exp -1) for which the remnant is just beginning to go radiative. Assuming SNRs evolve in a warm phase dominated ISM, we find dust destruction timescales are increased by a factor of approximately 2 compared to those of Jones et al. (1996), who assumed a hot gas dominated ISM. Recent estimates of supernova rates and ISM mass lead to another factor of approximately 3 increase in the destruction timescales, resulting in a silicate grain destruction timescale of approximately 2-3 Gyr. These increases, while not able resolve the problem of the discrepant timescales for silicate grain destruction and creation, are an important step towards understanding the origin, and evolution of dust in the ISM.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN21288 , The Astrophysical Journal (e-ISSN 1538-4357); 803; 1; 7
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 66
    facet.materialart.
    Unknown
    Complete Tem-Tomography: 3D Structure of Gems Cluster (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: GEMS (glass with embedded metal and sulfide) grains in interplanetary dust particles (IDPs) are considered to be one of the ubiquitous and fundamental building blocks of solids in the Solar System. They have been considered to be interstellar silicate dust that survived various metamorphism or alteration processes in the protoplanetary disk but the elemental and isotopic composition measurements suggest that most of them have been formed in the protoplanetary disk as condensates from high temperature gas. This formation model is also supported by the formation of GEMS-like grains with respect to the size, mineral assemblage, texture and infrared spectrum by condensation experiments from mean GEMS composition materials. Previous GEMS studies were performed only with 2D observation by transmission electron microscopy (TEM) or scanning TEM (STEM). However, the 3D shape and structure of GEMS grains and the spatial distribution of Fe/FeS's has critical information about their formation and origin. Recently, the 3D structure of GEMS grains in ultrathin sections of cluster IDPs was revealed by electron tomography using a TEM/STEM (JEM-2100F, JEOL). However, CT images of thin sections mounted on Cu grids acquired by conventional TEM-tomography are limited to low tilt angles (e. g., less than absolute value of 75 deg. In fact, previous 3D TEM observations of GEMS were affected by some artifacts related to the limited tilt range in the TEM used. Complete tomographic images should be acquired by rotating the sample tilt angle over a range of more than absolute value of 80 deg otherwise the CT images lose their correct structures. In order to constrain the origin and formation process of GEMS grains more clearly, we performed complete electron tomography for GEMS grains. Here we report the sample preparation method we have developed for this study, and the preliminary results.
    Keywords: Astrophysics
    Type: JSC-CN-32847 , Lunar and Planetary Science Conference; Mar 16, 2015 - Mar 20, 2015; The Woodlands, TX; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 67
    facet.materialart.
    Unknown
    A Procedure to Simultaneously Determine the Calcium, Chromium, and Titanium Isotopic Compositions of Astromaterials (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Many elements display both linear (mass-dependent) and non-linear (mass-independent) isotope anomalies (relative to a common reservoir). In early Solar System objects, with the exception of oxygen, mass-dependent isotope anomalies are most commonly thought to result from phase separation processes such as evaporation and condensation, whereas many mass-independent isotope anomalies likely reflect radiogenic ingrowth or incomplete mixing of presolar components in the proto-planetary disk. Coupling the isotopic characterization of multiple elements with differing volatilities in single objects may provide information regarding the location, source material, and/or processes involved in the formation of early Solar System solids. Here, we follow up on the work presented in, and detail new procedures developed to make high-precision multi-isotope measurements of Calcium, Chromium, and Titanium with small or limited amounts of sample using thermal ionization mass spectrometry and multi-collector ICP-MS, and characterize a suite of chondritic and terrestrial standards.
    Keywords: Astrophysics
    Type: JSC-CN-32817 , Lunar and Planetary Science Conference; Mar 16, 2015 - Mar 20, 2015; The Woodlands, TX; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 68
    facet.materialart.
    Unknown
    Early Size Distributions of Chondrule Subgroups Overprinted by the Final Accumulation Process of Particle Components in Allende (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Populations of compositionally distinct particles are fundamental components of undifferentiated chondritic meteorites. Many theories explain the formation of chondrites, one class of which includes mechanisms for sorting the component particles in the solar nebula prior to their accretion. Mechanisms include sorting by mass, turbulent concentration, X-winds, and photophoresis, which will produce characteristic distributions of observable properties such as particle size. Distinguishing processes that occur in specific astrophysical environments requires characterization of particle types, which include refractory Ca-Al-rich Inclusions (CAIs) and less-refractory chondrules. Previous investigations of modal abundances of CAIs and chondrules exist, but differences within and between these two groups, both of which are made up of diverse subgroups with different thermal histories and chemical compositions, remain mostly unstudied. The presence of rims, a significant event occurring after the formation of at least some chondrules, have also yet to be considered with respect to sorting. Here we present the sizes of CAIs and chondrules in Allende with attention to the smallest sizes, subgroups, and particle rims.
    Keywords: Astrophysics
    Type: JSC-CN-32809 , Lunar and Planetary Science Conference; Mar 16, 2015 - Mar 20, 2015; The Woodlands, TX; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 69
    facet.materialart.
    Unknown
    Constraining the Physics of AM Canum Venaticorum Systems with the Accretion Disk Instability Model (2015)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Recent work by Levitan et al. has expanded the long-term photometric database for AM CVn stars. In particular, their outburst properties are well correlated with orbital period and allow constraints to be placed on the secular mass transfer rate between secondary and primary if one adopts the disk instability model for the outbursts. We use the observed range of outbursting behavior for AM CVn systems as a function of orbital period to place a constraint on mass transfer rate versus orbital period. We infer a rate approximately 5 x 10(exp -9) solar mass yr(exp -1) ((P(sub orb)/1000 s)(exp -5.2)). We show that the functional form so obtained is consistent with the recurrence time-orbital period relation found by Levitan et al. using a simple theory for the recurrence time. Also, we predict that their steep dependence of outburst duration on orbital period will flatten considerably once the longer orbital period systems have more complete observations.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN34675 , The Astrophysical Journal (e-ISSN 1538-4357); 803; 1; 19
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 70
    facet.materialart.
    Unknown
    ANTARES Constrains a Blazar Origin of Two IceCube PeV Neutrino Events (2015)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Context. The source(s) of the neutrino excess reported by the IceCube Collaboration is unknown. The TANAMI Collaboration recently reported on the multiwavelength emission of six bright, variable blazars which are positionally coincident with two of the most energetic IceCube events. Objects like these are prime candidates to be the source of the highest-energy cosmic rays, and thus of associated neutrino emission. Aims. We present an analysis of neutrino emission from the six blazars using observations with the ANTARES neutrino telescope. Methods. The standard methods of the ANTARES candidate list search are applied to six years of data to search for an excess of muons - and hence their neutrino progenitors - from the directions of the six blazars described by the TANAMI Collaboration, and which are possibly associated with two IceCube events. Monte Carlo simulations of the detector response to both signal and background particle fluxes are used to estimate the sensitivity of this analysis for di erent possible source neutrino spectra. A maximum-likelihood approach, using the reconstructed energies and arrival directions of through-going muons, is used to identify events with properties consistent with a blazar origin. Results. Both blazars predicted to be the most neutrino-bright in the TANAMI sample (1653-329 and 1714-336) have a signal flux fitted by the likelihood analysis corresponding to approximately one event. This observation is consistent with the blazar-origin hypothesis of the IceCube event IC 14 for a broad range of blazar spectra, although an atmospheric origin cannot be excluded. No ANTARES events are observed from any of the other four blazars, including the three associated with IceCube event IC20. This excludes at a 90% confidence level the possibility that this event was produced by these blazars unless the neutrino spectrum is flatter than -2.4.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN34645 , Astronomy & Astrophysics (e-ISSN 1432-0746); 576; L8
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 71
    facet.materialart.
    Unknown
    The Cosmology Large Angular Scale Surveyor (CLASS) (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Cosmology Large Angular Scale Surveyor (CLASS) is a four telescope array designed to characterize relic primordial gravitational waves from in ation and the optical depth to reionization through a measurement of the polarized cosmic microwave background (CMB) on the largest angular scales. The frequencies of the four CLASS telescopes, one at 38 GHz, two at 93 GHz, and one dichroic system at 145/217 GHz, are chosen to avoid spectral regions of high atmospheric emission and span the minimum of the polarized Galactic foregrounds: synchrotron emission at lower frequencies and dust emission at higher frequencies. Low-noise transition edge sensor detectors and a rapid front-end polarization modulator provide a unique combination of high sensitivity, stability, and control of systematics. The CLASS site, at 5200 m in the Chilean Atacama desert, allows for daily mapping of up to 70% of the sky and enables the characterization of CMB polarization at the largest angular scales. Using this combination of a broad frequency range, large sky coverage, control over systematics, and high sensitivity, CLASS will observe the reionization and recombination peaks of the CMB E- and B-mode power spectra. CLASS will make a cosmic variance limited measurement of the optical depth to reionization and will measure or place upper limits on the tensor-to-scalar ratio, r, down to a level of 0.01 (95% C.L.).
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN35081 , Proc. of SPIE, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy (ISSN 0277-786X); 9914; 99141K|Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy; Jun 26, 2016 - Jul 01, 2016; Edinburgh; United Kingdom
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 72
    facet.materialart.
    Unknown
    SpIES: The Spitzer IRAC Equatorial Survey (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We describe the first data release from the Spitzer-IRAC Equatorial Survey (SpIES); a large-area survey of approx.115 sq deg in the Equatorial SDSS Stripe 82 field using Spitzer during its "warm" mission phase. SpIES was designed to probe sufficient volume to perform measurements of quasar clustering and the luminosity function at z 〉 or = 3 to test various models for "feedback" from active galactic nuclei (AGNs). Additionally, the wide range of available multi-wavelength, multi-epoch ancillary data enables SpIES to identify both high-redshift (z 〉 or = 5) quasars as well as obscured quasars missed by optical surveys. SpIES achieves 5 sigma depths of 6.13 Jy (21.93 AB magnitude) and 5.75 Jy (22.0 AB magnitude) at 3.6 and 4.5 microns, respectively-depths significantly fainter than the Wide-field Infrared Survey Explorer (WISE). We show that the SpIES survey recovers a much larger fraction of spectroscopically confirmed quasars (approx.98%) in Stripe 82 than are recovered by WISE (55%). This depth is especially powerful at high-redshift (z 〉 or = 3.5), where SpIES recovers 94% of confirmed quasars, whereas WISE only recovers 25%. Here we define the SpIES survey parameters and describe the image processing, source extraction, and catalog production methods used to analyze the SpIES data. In addition to this survey paper, we release 234 images created by the SpIES team and three detection catalogs: a 3.6 microns only detection catalog containing approx. 6.1 million sources, a 4.5 microns only detection catalog containing approx. 6.5 million sources, and a dual-band detection catalog containing approx. 5.4 million sources.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN35054 , The Astrophysical Journal Supplement Series; 225; 1; 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 73
    facet.materialart.
    Unknown
    Periodic Eclipse Variations in Asynchronous Polar V1432 Aql: Evidence of a Shifting Threading Region (2015)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We report the results of a 28-month photometric campaign studying V1432 Aql, the only known eclipsing, asynchronous polar. Our data show that both the residual eclipse flux and eclipse OC timings vary strongly as a function of the spin-orbit beat period. Relying upon a new model of the system, we show that cyclical changes in the location of the threading region along the ballistic trajectory of the accretion stream could produce both effects. This model predicts that the threading radius is variable, in contrast to previous studies which have assumed a constant threading radius. Additionally, we identify a very strong photometric maximum which is only visible for half of the beat cycle. The exact cause of this maximum is unclear, but we consider the possibility that it is the optical counterpart of the third accreting polecap proposed by Rana et al. Finally, the rate of change of the white dwarf's spin period is consistent with it being proportional to the difference between the spin and orbital periods, implying that the spin period is approaching the orbital period asymptotically.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN35009 , Monthly Notices of the Royal Astronomical Society (ISSN 0035-8711) (e-ISSN 1365-2966); 449; 3; 3107-3120
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 74
    facet.materialart.
    Unknown
    Determining the Covering Factor of Compton-Thick Active Galactic Nuclei with NuSTAR (2015)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The covering factor of Compton-thick (CT) obscuring material associated with the torus in active galactic nuclei (AGNs) is at present best understood through the fraction of sources exhibiting CT absorption along the line of sight (N(sub H) greater than 1.5 x 10(exp 24) cm(exp 2)) in the X-ray band, which reveals the average covering factor. Determining this CT fraction is difficult, however, due to the extreme obscuration. With its spectral coverage at hard X-rays (greater than 10 keV), Nuclear Spectroscopic Telescope Array (NuSTAR) is sensitive to the AGNs covering factor since Compton scattering of X-rays off optically thick material dominates at these energies. We present a spectral analysis of 10 AGNs observed with NuSTAR where the obscuring medium is optically thick to Compton scattering, so-called CT AGNs. We use the torus models of Brightman and Nandra that predict the X-ray spectrum from reprocessing in a torus and include the torus opening angle as a free parameter and aim to determine the covering factor of the CT gas in these sources individually. Across the sample we find mild to heavy CT columns, with N(sub H) measured from 10(exp 24) to 10(exp 26) cm(exp 2), and a wide range of covering factors, where individual measurements range from 0.2 to 0.9. We find that the covering factor, f(sub c), is a strongly decreasing function of the intrinsic 2-10 keV luminosity, L(sub X), where f(sub c) = (0.41 +/- 0.13)log(sub 10)(L(sub X)/erg s(exp 1))+18.31 +/- 5.33, across more than two orders of magnitude in L(sub X) (10(exp 41.5) - 10(exp 44) erg s(exp 1)). The covering factors measured here agree well with the obscured fraction as a function of LX as determined by studies of local AGNs with L(sub X) greater than 10(exp 42.5) erg s(exp 1).
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN35028 , The Astrophysical Journal; 805; 1; 41
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 75
    facet.materialart.
    Unknown
    Ti-44 Gamma-Ray Emission Lines from SN1987A Reveal an Asymmetric Explosion (2015)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: In core-collapse supernovae, titanium-44 (Ti-44) is produced in the innermost ejecta, in the layer of material directly on top of the newly formed compact object. As such, it provides a direct probe of the supernova engine. Observations of supernova 1987A (SN1987A) have resolved the 67.87- and 78.32-kilo-electron volt emission lines from decay of Ti-44 produced in the supernova explosion. These lines are narrow and redshifted with a Doppler velocity of ~700 kilometers per second, direct evidence of large-scale asymmetry in the explosion.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN34983 , Science Magazine (e-ISSN 1095-9203); 348; 6235; 670-671
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 76
    facet.materialart.
    Unknown
    X-Ray Surveyor - The Beginning (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Astrophysics
    Type: MSFC-E-DAA-TN33175 , SPIE Astronomical Telescopes and Instrumentation Conference; Jun 26, 2016 - Jul 01, 2016; Edinburgh; United Kingdom
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 77
    facet.materialart.
    Unknown
    Space Detectors for Gamma Rays (100 MeV-100 GeV): from Egret to Fermi LAT (2015)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The design of spaceborne high-energy (E is greater than 100 MeV) gamma-ray detectors depends on two principal factors: (1) the basic physics of detecting and measuring the properties of the gamma rays; and (2) the constraints of operating such a detector in space for an extended period. Improvements in technology have enabled major advances in detector performance, as illustrated by two successful instruments, EGRET on the Compton Gamma Ray Observatory and LAT on the Fermi Gamma-ray Space Telescope.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN32820 , Comptes Rendus Physique (ISSN 1631-0705); 16; 7-Jun; 600-609
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 78
    facet.materialart.
    Unknown
    Galaxy Evolution Spectroscopic Explorer: Scientific Rationale (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: GESE is a mission concept consisting of a 1.5-m space telescope and UV multi-object slit spectrograph designed to help understand galaxy evolution in a critical era in the history of the universe, where the rate of star-formation stopped increasing and started to decline. To isolate and identify the various processes driving the evolution of these galaxies, GESE will obtain rest-frame far-UV spectra of 100,000 galaxies at redshifts, z approximately 1-2. To obtain such a large number of spectra, multiplexing over a wide field is an absolute necessity. A slit device such as a digital micro-mirror device (DMD) or a micro-shutter array (MSA) enables spectroscopy of a hundred or more sources in a single exposure while eliminating overlapping spectra of other sources and blocking unwanted background like zodiacal light. We find that a 1.5-m space telescope with a MSA slit device combined with a custom orbit enabling long, uninterrupted exposures (approximately 10 hr) are optimal for this spectroscopic survey. GESE will not be operating alone in this endeavor. Together with x-ray telescopes and optical/near-IR telescopes like Subaru/Prime Focus Spectrograph, GESE will detect "feedback" from young massive stars and massive black holes (AGN's), and other drivers of galaxy evolution.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN35215 , Proceedings of SPIE, Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray; 9905; 990505
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 79
    facet.materialart.
    Unknown
    Foreground Bias from Parametric Models of Far-IR Dust Emission (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We use simple toy models of far-IR dust emission to estimate the accuracy to which the polarization of the cosmic microwave background can be recovered using multi-frequency fits, if the parametric form chosen for the fitted dust model differs from the actual dust emission. Commonly used approximations to the far-IR dust spectrum yield CMB residuals comparable to or larger than the sensitivities expected for the next generation of CMB missions, despite fitting the combined CMB plus foreground emission to precision 0.1 percent or better. The Rayleigh-Jeans approximation to the dust spectrum biases the fitted dust spectral index by (Delta)(Beta)(sub d) = 0.2 and the inflationary B-mode amplitude by (Delta)(r) = 0.03. Fitting the dust to a modified blackbody at a single temperature biases the best-fit CMB by (Delta)(r) greater than 0.003 if the true dust spectrum contains multiple temperature components. A 13-parameter model fitting two temperature components reduces this bias by an order of magnitude if the true dust spectrum is in fact a simple superposition of emission at different temperatures, but fails at the level (Delta)(r) = 0.006 for dust whose spectral index varies with frequency. Restricting the observing frequencies to a narrow region near the foreground minimum reduces these biases for some dust spectra but can increase the bias for others. Data at THz frequencies surrounding the peak of the dust emission can mitigate these biases while providing a direct determination of the dust temperature profile.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN35232 , The Astrophysical Journal (e-ISSN 2041-8213); 826; 2; 101
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 80
    facet.materialart.
    Unknown
    Ogle-2012-blg-0724lb: A Saturn Mass Planet Around an M-dwarf (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We report the discovery of a planet by the microlensing method, OGLE-2012-BLG-0724Lb. Although the duration of the planetary signal for this event was one of the shortest seen for a planetary event, the anomaly was well covered thanks to high-cadence observations taken by the survey groups OGLE and MOA. By analyzing the light curve, this planetary system is found to have a mass ratio q = (1.58 +/- 0.15) x 10(exp -3). By conducting a Bayesian analysis, we estimate that the host star is an M dwarf with a mass of M(sub L) = 0.29(+0.33/-0.16) solar mass located at D(sub L) = 6.7(+1.1/-1.2) kpc away from the Earth and the companion's mass is m(sub P) = 0.47(+0.54/-0.26) M(Jup). The projected planet- host separation is a falsum = 1.6(+0.4/-0.3) AU. Because the lens-source relative proper motion is relatively high, future highresolution images would detect the lens host star and determine the lens properties uniquely. This system is likely a Saturn-mass exoplanet around an M dwarf, and such systems are commonly detected by gravitational microlensing. This adds another example of a possible pileup of sub-Jupiters (0.2 less than m(sub P)/M(sub Jup) less than 1) in contrast to a lack of Jupiters (approximately 1-2 M(sub Jup)) around M dwarfs, supporting the prediction by core accretion models that Jupiter-mass or more massive planets are unlikely to form around M dwarfs.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN33865 , The Astrophysical Journal; 824; 2; 139
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 81
    facet.materialart.
    Unknown
    Lithium Inventory of 2 Solar Mass Red Clump Stars in Open Clusters: A Test of the Helium Flash Mechanism (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The temperature distribution of field Li-rich red giants suggests the presence of a population of Li-rich red clump (RC) stars. One proposed explanation for this population is that all stars with masses near 2 solar mass experience a shortlived phase of Li-richness at the onset of core He-burning. Many of these stars have low C-12/C-13, a signature of deep mixing that is presumably associated with the Li regeneration. To test this purported mechanism of Li enrichment, we measured abundances in 38 RC stars and 6 red giant branch (RGB) stars in four open clusters selected to have RC masses near 2 solar mass. We find six Li-rich stars (A(Li) greater than or equal to 1.50 dex) of which only two may be RC stars. None of the RC stars have Li exceeding the levels observed in the RGB stars, but given the brevity of the suggested Li-rich phase and the modest sample size, it is probable that stars with larger Li-enrichments were missed simply by chance. However, we find very few stars in our sample with low C-12/C-13. Such low C-12/C-13, seen in many field Li-rich stars, should persist even after lithium has returned to normal low levels. Thus, if Li synthesis during the He flash occurs, it is a rare, but potentially long-lived occurrence rather than a short-lived phase for all stars. We estimate a conservative upper limit of the fraction of stars going through a Li-rich phase to be less than 47%, based on stars that have low C-12/C-13 for their observed A(Li).
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN35147 , The Astrophysical Journal; 827; 2; 129
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 82
    facet.materialart.
    Unknown
    Near-IR Polarized Scattered Light Imagery of the DoAr 28 Transitional Disk (2015)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We present the first spatially resolved polarized scattered light H-band detection of the DoAr 28 transitional disk. Our two epochs of imagery detect the scattered light disk from our effective inner working angle of 0 double prime.10 (13 AU) out to 0double prime.50 (65 AU). This inner working angle is interior to the location of the system's gap inferred by previous studies using spectral energy distribution modeling (15 AU). We detected a candidate point source companion 1 double prime.08 northwest of the system; however, our second epoch of imagery strongly suggests that this object is a background star. We constructed a grid of Monte Carlo Radiative Transfer models of the system, and our best fit models utilize a modestly inclined (50 degrees), 0.01 solar mass disk that has a partially depleted inner gap from the dust sublimation radius out to approximately 8 AU. Subtracting this best fit, axi-symmetric model from our polarized intensity data reveals evidence for two small asymmetries in the disk, which could be attributable to a variety of mechanisms.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN32942 , The Astronomical Journal; 150; 86; 86
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 83
    facet.materialart.
    Unknown
    A Giant Radio Halo in a Low-Mass SZ-Selected Galaxy Cluster: ACT-CL J0256.5+0006 (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We present the detection of a giant radio halo (GRH) in the Sunyaev-Zel'dovich (SZ)-selected merging galaxy cluster ACT-CL J0256.5+0006 (zeta = 0.363), observed with the Giant Metrewave Radio Telescope at 325 MHz and 610 MHz. We find this cluster to host a faint (S(sub 610) = 5.6 +/- 1.4 mJy) radio halo with an angular extent of 2.6 arcmin, corresponding to 0.8 Mpc at the cluster redshift, qualifying it as a GRH. J0256 is one of the lowest-mass systems, M(sub 500,SZ) = (5.0 +/- 1.2) x 10(sup14) solar mass foud to host a GRH. We measure the GRH at lower significance at 325 MHz (S(sub 325) = 10.3 +/- 5.3 mJy), obtaining a spectral index measurement of alpha sup 610 sub 325 = 1.0(sup +0.7)(sub 0.9). This result is consistent with the mean spectral index of the population of typical radio halos, alpha = 1.2 +/- 0.2. Adopting the latter value, we determine a 1.4 GHz radio power of P(sub 1.4GHz) = (1.0 +/- 03) x 10(sup 24) W Hz(sup -1), placing this cluster within the scatter of known scaling relations. Various lines of evidence, including the ICM morphology, suggest that ACT-CL J0256.5+0006 is composed of two subclusters. We determine a merger mass ratio of 7:4, and a line-of-sight velocity difference of perpendicular = 1880 +/- 210 km s(sup -1). We construct a simple merger model of infer relevant time-scales in the merger. From its location on the P1.4GHz-L(sub x) scaling relation, we infer that we observe ACT-CL J0256.5+0006 just before first core crossing.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN32419 , Monthly Notices Letters of the Royal Astronomical Observatory (e-ISSN 1745-3933); 459; 4; 4240-4258
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 84
    facet.materialart.
    Unknown
    Advanced ACTPol Cryogenic Detector Arrays and Readout (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Advanced ACTPol is a polarization-sensitive upgrade for the 6 m aperture Atacama Cosmology Telescope, adding new frequencies and increasing sensitivity over the previous ACTPol receiver. In 2016, Advanced ACTPol will begin to map approximately half the sky in five frequency bands (28-230 GHz). Its maps of primary and secondary cosmic microwave background anisotropies-imaged in intensity and polarization at few arcminute-scale resolution-will enable precision cosmological constraints and also awide array of cross-correlation science that probes the expansion history of the universe and the growth of structure via gravitational collapse. To accomplish these scientific goals, the AdvancedACTPol receiver will be a significant upgrade to the ACTPol receiver, including four new multichroic arrays of cryogenic, feedhorn-coupled AlMn transition edge sensor polarimeters (fabricated on 150 mm diameter wafers); a system of continuously rotating meta-material silicon half-wave plates; and a new multiplexing readout architecture which uses superconducting quantum interference devices and time division to achieve a 64-row multiplexing factor. Here we present the status and scientific goals of the Advanced ACTPol instrument, emphasizing the design and implementation of the AdvancedACTPol cryogenic detector arrays.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN32121 , Journal of Low Temperature Physics (ISSN 0022-2291) (e-ISSN 1573-7357); 1-8
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 85
    facet.materialart.
    Unknown
    AlMn Transition Edge Sensors for Advanced ACTPol (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Advanced ACTPol (Adv ACT) will use an array of multichroic polarization sensitive AIMn transition edge sensor (TES) bolometers read out through time-division multiplexing. Aluminum doped with a low concentration of manganese can be deposited to a bulk film thickness for a more reliable superconducting critical temperature uniformity compared to thin bilayers. To build the TES, the AlMn alloy is deposited, over Nb wiring, to a specific thickness to set the TES normal resistance. The doping concentration of manganese coarsely defines the TES critical temperature, while a fine tuning is achieved by heating the deposited film to a specific temperature. The TES island is connected to the thermal bath via four silicon-nitride membranes, where their geometry defines the thermal conductance to the temperature of the bath. Lastly, the TES heat capacity is increased by addition of PdAu electrically connected to the AlMn film. Designs and performance characteristics of these AlMn TESs are presented for use in AdvACT.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN32110 , Journal of Low Temperature Physics; 184; 2-Jan; 66-73
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 86
    facet.materialart.
    Unknown
    The Brief but Long Life of X-ray Polarimetry (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Astrophysics
    Type: MSFC-E-DAA-TN32097 , The First Science Conference on the IXPE Mission; May 24, 2016 - May 26, 2016; Valencia; Spain
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 87
    facet.materialart.
    Unknown
    Evolution of the Far-Infrared Cloud at Titan's South Pole (2015)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A condensate cloud on Titan identified by its 220 cm1 far-infrared signature continues to undergo seasonal changes at both the north and south poles. In the north, the cloud, which extends from 55 N to the pole, has been gradually decreasing in emission intensity since the beginning of the Cassini mission with a half-life of 3.8 years. The cloud in the south did not appear until 2012 but its intensity has increased rapidly, doubling every year. The shape of the cloud at the south pole is very different from that in the north. Mapping in 2013 December showed that the condensate emission was confined to a ring with a maximum at 80 S. The ring was centered 4deg from Titans pole. The pattern of emission from stratospheric trace gases like nitriles and complex hydrocarbons (mapped in 2014 January) was also offset by 4deg, but had a central peak at the pole and a secondary maximum in a ring at about 70 S with a minimum at 80 S. The shape of the gas emission distribution can be explained by abundances that are high at the atmospheric pole and diminish toward the equator, combined with correspondingly increasing temperatures. We discuss possible causes for the condensate ring. The present rapid build up of the condensate cloud at the south pole is likely to transition to a gradual decline from 2015 to 2016. Key words: molecular processes - planets and satellites: atmospheres - planets and satellites: composition - planets and satellites: individual (Titan) - radiation mechanisms: thermal
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN31332 , Astrophysical Journal Letters (e-ISSN 2041-8213); 804; 2; L34
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 88
    facet.materialart.
    Unknown
    Extended Hard-X-Ray Emission in the Inner Few Parsecs of the Galaxy (2015)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Galactic Centre hosts a puzzling stellar population in its inner few parsecs, with a high abundance of surprisingly young, relatively massive stars bound within the deep potential well of the central supermassive black hole, Sagittarius A* (ref. 1). Previous studies suggest that the population of objects emitting soft X-rays (less than 10 kiloelectronvolts) within the surrounding hundreds of parsecs, as well as the population responsible for unresolved X-ray emission extending along the Galactic plane, is dominated by accreting white dwarf systems2, 3, 4, 5.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN30997 , Nature: International Weekly Journal of Science (e-ISSN 1476-4687); 520; 7549; 646-649
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 89
    facet.materialart.
    Unknown
    The Variable Crab Nebula: Evidence for a Connection Between GeV Flares and Hard X-ray Variations (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In 2010, hard X-ray variations (Wilson-Hodge et al. 2011) and GeV flares (Tavani et al 2011, Abdo et al. 2011) from the Crab Nebula were discovered. Connections between these two phenomena were unclear, in part because the timescales were quite different, with yearly variations in hard X-rays and hourly to daily variations in the GeV flares. The hard X-ray flux from the Crab Nebula has again declined since 2014, much like it did in 2008-2010. During both hard X-ray decline periods, the Fermi LAT detected no GeV flares, suggesting that injection of particles from the GeV flares produces the much slower and weaker hard X-ray variations. The timescale for the particles emitting the GeV flares to lose enough energy to emit synchrotron photons in hard X-rays is consistent with the yearly variations observed in hard X-rays and with the expectation that the timescale for variations slowly increases with decreasing energy. This hypothesis also predicts even slower and weaker variations below 10 keV, consistent with the non-detection of counterparts to the GeV flares by Chandra (Weisskopf et al 2013). We will present a comparison of the observed hard X-ray variations and a simple model of the decay of particles from the GeV flares to test our hypothesis.
    Keywords: Astrophysics
    Type: MSFC-E-DAA-TN31003 , High Energy Astrophysics (HEAD) Divisional Meeting; Apr 03, 2016 - Apr 07, 2016; Naples, FL; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 90
    facet.materialart.
    Unknown
    Feedhorn-Coupled Transition-Edge Superconducting Bolometer Arrays for Cosmic Microwave Background Polarimetry (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: NIST produces large-format, dual-polarization-sensitive detector arrays for a broad range of frequencies (30-1400 GHz). Such arrays enable a host of astrophysical measurements. Detectors optimized for cosmic microwave background observations are monolithic, polarization-sensitive arrays based on feedhorn and planar Nb antenna-coupled transition-edge superconducting (TES) bolometers. Recent designs achieve multiband, polarimetric sensing within each spatial pixel. In this proceeding, we describe our multichroic, feedhorn-coupled design; demonstrate performance at 70-380 GHz; and comment on current developments for implementation of these detector arrays in the advanced Atacama Cosmology Telescope receiver
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN32074 , International Symposium on Space Terahertz Technology; Mar 16, 2015 - Mar 18, 2015; Cambridge, MA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 91
    facet.materialart.
    Unknown
    Modular Mirror Assembly Systems Engineering (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Goal: Consider design challenges for X-Ray Surveyor beyond mirror segment fabrication and mounting. Unique challenges for modular Mirror Assembly.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN30871 , X-Ray Surveyor Workshop; Mar 28, 2016; College Park, MD; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 92
    facet.materialart.
    Unknown
    Lithium in Open Cluster Red Giants Hosting Substellar Companions (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We have measured stellar parameters, [Fe/H], lithium abundances, rotation, and (12)C/13C in a small sample of red giants (RGs) in three open clusters that are each home to a RG star that hosts a substellar companion (SSC) (NGC 2423 3, NGC 4349 127, and BD+12 1917 in M67). Our goal is to explore whether the presence of SSCs influences the Li content. Both (12)C/13C and stellar rotation are measured as additional tracers of stellar mixing. One of the companion hosts, NGC 24233, is found to be Li-rich with A(Li)(sub NLTE) = 1.56 dex, and this abundance is significantly higher than the A(Li) of the two comparison stars in NGC 2423. All three SSC hosts have the highest A(Li) and (12)C/13C when compared to the control RGs in their respective clusters; however, except for NGC 24233, at least one control star has similarly high abundances within the uncertainties. Higher A(Li) could suggest that the formation or presence of planets plays a role in the degree of internal mixing on or before the RG branch. However, a multitude of factors affect A(Li) during the RG phase, and when the abundances of our sample are compared with the abundances of RGs in other open clusters available in the literature, we find that they all fall well within a much larger distribution of A(Li) and (12)C/13C. Thus, even the high Li in NGC 2423 3 cannot be concretely tied to the presence of the SSC.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN30763 , The Astrophysical Journal (e-ISSN 2041-8213); 818; 1; 25
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 93
    facet.materialart.
    Unknown
    The LEAP Gamma-Ray Burst Polarimeter for the International Space Station (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Astrophysics
    Type: MSFC-E-DAA-TN30447 , Physics Seminar; Mar 08, 2016; Huntsville, AL; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 94
    facet.materialart.
    Unknown
    When a Standard Candle Flickers: Hard X-Ray Variations in the Crab Nebula (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Astrophysics
    Type: MSFC-E-DAA-TN20105 , American Astronomical Society Meeting; Jan 04, 2015 - Jan 08, 2015; Seattle, WA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 95
    facet.materialart.
    Unknown
    Light-Curve Modelling Constraints on the Obliquities and Aspect Angles of the Young Fermi Pulsars (2015)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: In more than four years of observation the Large Area Telescope on board the Fermi satellite has identified pulsed gamma-ray emission from more than 80 young or middle-aged pulsars, in most cases providing light curves with high statistics. Fitting the observed profiles with geometrical models can provide estimates of the magnetic obliquity alpha and of the line of sight angle zeta, yielding estimates of the radiation beaming factor and radiated luminosity. Using different gamma-ray emission geometries (Polar Cap, Slot Gap, Outer Gap, One Pole Caustic) and core plus cone geometries for the radio emission, we fit gamma-ray light curves for 76 young or middle-aged pulsars and we jointly fit their gamma-ray plus radio light curves when possible. We find that a joint radio plus gamma-ray fit strategy is important to obtain (alpha, zeta) estimates that can explain simultaneously detectable radio and gamma-ray emission: when the radio emission is available, the inclusion of the radio light curve in the fit leads to important changes in the (alpha, gamma) solutions. The most pronounced changes are observed for Outer Gap and One Pole Caustic models for which the gamma-ray only fit leads to underestimated alpha or zeta when the solution is found to the left or to the right of the main alpha-zeta plane diagonal respectively. The intermediate-to-high altitude magnetosphere models, Slot Gap, Outer Gap, and One pole Caustic, are favored in explaining the observations. We find no apparent evolution of on a time scale of 106 years. For all emission geometries our derived gamma-ray beaming factors are generally less than one and do not significantly evolve with the spin-down power. A more pronounced beaming factor vs. spin-down power correlation is observed for Slot Gap model and radio-quiet pulsars and for the Outer Gap model and radio-loud pulsars. The beaming factor distributions exhibit a large dispersion that is less pronounced for the Slot Gap case and that decreases from radio-quiet to radio-loud solutions. For all models, the correlation between gamma-ray luminosity and spin-down power is consistent with a square root dependence. The gamma-ray luminosities obtained by using the beaming factors estimated in the framework of each model do not exceed the spin-down power. This suggests that assuming a beaming factor of one for all objects, as done in other studies, likely overestimates the real values. The data show a relation between the pulsar spectral characteristics and the width of the accelerator gap. The relation obtained in the case of the Slot Gap model is consistent with the theoretical prediction.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN28751 , Astronomy & Astrophysics; 575; A3; 88
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 96
    facet.materialart.
    Unknown
    Program Technology Gaps A Presentation to the Mirror Tech 2015 Workshop (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This talk will discuss the span of highest priority technologies for both astrophysics programs: what the top technology need categories are; competed lines available; what we are already funding.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN27930 , Mirror Technology Workshop 2015; Nov 10, 2015 - Nov 12, 2015; Annapolis, MD; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 97
    facet.materialart.
    Unknown
    Comparing and Contrasting Detectors: JWST NIR vs HST WFC3 (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In many ways, WFC3s IR channel is a good indicator for what to expect with JWST. There are some differences, most of which should be beneficial in JWST- JWSTs lower operating temperature will freeze out charge traps that would affect WFC3. Benefits should include lower dark current, lower persistence, and better reciprocity- JWSTs more recent HgCdTe process has lower defect density. The benefits are as described above- JWST uses better indium barriers. The benefits should include fewer RC type pixels. One area where more study might be beneficial is stability. The detector electronics play a significant role in determining how stable a detector system is(v.s. bias drifts and photometry). JWSTs SIDECARs are completely WFC3s Ball electronics- Studies comparing the bias and photometric stability of WFC3 and JWST might be useful to informing data acquisition and calibration strategies for JWST.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN28105 , Enabling Transiting Exoplanet Science with JWST Workshop; Nov 16, 2015 - Nov 18, 2015; Baltimore, MD; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 98
    facet.materialart.
    Unknown
    A Coordinated X-Ray and Optical Campaign of the Nearest Massive Eclipsing Binary, Delta Orionis Aa. I. Overview of the X-Ray Spectrum (2015)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We present an overview of four deep phase-constrained Chandra HETGS X-ray observations of Delta Ori A. Delta Ori A is actually a triple system that includes the nearest massive eclipsing spectroscopic binary, Delta Ori Aa, the only such object that can be observed with little phase-smearing with the Chandra gratings. Since the fainter star, Delta Ori Aa2, has a much lower X-ray luminosity than the brighter primary (Delta Ori Aa1), Delta Ori Aa provides a unique system with which to test the spatial distribution of the X-ray emitting gas around Delta Ori Aa1 via occultation by the photosphere of, and wind cavity around, the X-ray dark secondary. Here we discuss the X-ray spectrum and X-ray line profiles for the combined observation, having an exposure time of nearly 500 ks and covering nearly the entire binary orbit. The companion papers discuss the X-ray variability seen in the Chandra spectra, present new space-based photometry and ground-based radial velocities obtained simultaneously with the X-ray data to better constrain the system parameters, and model the effects of X-rays on the optical and UV spectra. We find that the X-ray emission is dominated by embedded wind shock emission from star Aa1, with little contribution from the tertiary star Ab or the shocked gas produced by the collision of the wind of Aa1 against the surface of Aa2. We find a similar temperature distribution to previous X-ray spectrum analyses. We also show that the line half-widths are about 0.30.5 times the terminal velocity of the wind of star Aa1. We find a strong anti-correlation between line widths and the line excitation energy, which suggests that longer-wavelength, lower-temperature lines form farther out in the wind. Our analysis also indicates that the ratio of the intensities of the strong and weak lines of Fe XVII and Ne X are inconsistent with model predictions, which may be an effect of resonance scattering.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN27991 , The Astrophysical Journal; 809; 2; 132
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 99
    facet.materialart.
    Unknown
    Fermi: The Gamma-Ray Large Area Telescope (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Following its launch in June 2008, high-energy gamma-ray observations by the Fermi Gamma-ray Space Telescope have unveiled over 1000 new sources and opened an important and previously unexplored window on a wide variety of phenomena. These have included the discovery of an population of pulsars pulsing only in gamma rays; the detection of photons up to 10s of GeV from gamma-ray bursts, enhancing our understanding of the astrophysics of these powerful explosions; the detection of hundreds of active galaxies; a measurement of the high energy cosmic-ray electron spectrum which may imply the presence of nearby astrophysical particle accelerators; the determination of the diffuse gamma-ray emission with unprecedented accuracy and the constraints on phenomena such as supersymmetric dark-matter annihilations and exotic relics from the Big Bang. Continuous monitoring of the high-energy gamma-ray sky has uncovered numerous outbursts from active galaxies and the discovery of transient sources in our galaxy. In this talk I will describe the current status of the Fermi observatory and review the science highlights from Fermi.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN24807 , International Cosmic Ray Conference (ICRC); Jul 30, 2015 - Aug 06, 2015; Hague; Netherlands
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 100
    facet.materialart.
    Unknown
    Ultraluminous X-Ray Sources in the Nearby Universe (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Astrophysics
    Type: MSFC-E-DAA-TN27583 , University of Alabama Huntsville Physics Seminars; Oct 20, 2015; Huntsville, AL; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...