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  • 1
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    First All-Sky Search for Continuous Gravitational Waves from Unknown Sources in Binary Systems (2014)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We present the first results of an all-sky search for continuous gravitational waves from unknown spinning neutron stars in binary systems using LIGO and Virgo data. Using a specially developed analysis program, the TwoSpect algorithm, the search was carried out on data from the sixth LIGO science run and the second and third Virgo science runs. The search covers a range of frequencies from 20 Hz to 520 Hz, a range of orbital periods from 2 to 2,254 h and a frequency- and period-dependent range of frequency modulation depths from 0.277 to 100 mHz. This corresponds to a range of projected semimajor axes of the orbit from 0.6 10(exp 3) ls to 6,500 ls assuming the orbit of the binary is circular. While no plausible candidate gravitational wave events survive the pipeline, upper limits are set on the analyzed data. The most sensitive 95% confidence upper limit obtained on gravitational wave strain is 2.3 10(exp 24) at 217 Hz, assuming the source waves are circularly polarized. Although this search has been optimized for circular binary orbits, the upper limits obtained remain valid for orbital eccentricities as large as 0.9. In addition, upper limits are placed on continuous gravitational wave emission from the low-mass x-ray binary Scorpius X-1 between 20 Hz and 57.25 Hz.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN22620 , Physical Review D (ISSN 0031-899X) (e-ISSN 1536-6065); 90; 6; 062010
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  • 2
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    Evidence for Gravitational Lensing of the Cosmic Microwave Background Polarization from Cross-Correlation with the Cosmic Infrared Background (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: We reconstruct the gravitational lensing convergence signal from Cosmic Microwave Background (CMB) polarization data taken by the Polarbear experiment and cross-correlate it with Cosmic Infrared Background (CIB) maps from the Herschel satellite. From the cross-spectra, we obtain evidence for gravitational lensing of the CMB polarization at a statistical significance of 4.0sigma and evidence for the presence of a lensing B-mode signal at a significance of 2.3sigma. We demonstrate that our results are not biased by instrumental and astrophysical systematic errors by performing null-tests, checks with simulated and real data, and analytical calculations. This measurement of polarization lensing, made via the robust cross-correlation channel, not only reinforces Polarbear auto-correlation measurements, but also represents one of the early steps towards establishing CMB polarization lensing as a powerful new probe of cosmology and astrophysics.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN15348 , Physical Review Letters (ISSN 0031-9007) (e-ISSN 1079-7114); 112; 13; 131302
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  • 3
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    Transitional Disks Associated With Intermediate-mass Stars: Results of the SEEDS YSO survey (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: As part of the Strategic Exploration of Exoplanets and Disks with Subaru YSO survey, we have surveyed a number of Herbig B-F stars at H-band using Polarimetric Differential Imaging+Angular differential imaging. Historically, Herbig stars have been sorted based on their IR SEDs into those with SEDS which can be fit by powerlaws over 1-200 m (Meeus et al. 2001, group II), and those which can be interpreted as a powerlaw + a blackbody component (Meeus group I) or powerlaw+missing warm thermal emission, which is one of the criteria for identification of gapped or transitional disks. Meeus group II disks, when imaged with HiCIAO show featureless disks with depolarization along the projection of the disk semi-minor axis (Kusakabe et al. 2012). This is what we had expected to see for the Meeus group I disks, except for the addition of wide gaps or central cavities. Instead we find wild diversity, suggesting that transitional disks are highly perturbed compared to Meeus group II disks.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN12714 , American Astronomical Society Meeting; Jan 05, 2014 - Jan 09, 2014; Washington, D.C.; United States
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  • 4
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    The Moving Group Targets of the Seeds High-Contrast Imaging Survey of Exoplanets and Disks: Results and Observations from the First Three Years (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: We present results from the first three years of observations of moving group (MG) targets in the Strategic Exploration of Exoplanets and Disks with Subaru (SEEDS) high-contrast imaging survey of exoplanets and disks using the Subaru telescope. We achieve typical contrasts of (is) approximately10(exp 5) at 1" and (is) approximately 10(exp 6) beyond 2" around 63 proposed members of nearby kinematic MGs. We review each of the kinematic associations to which our targets belong, concluding that five, beta Pictoris ((is) approximately 20 Myr), AB Doradus ((is) approximately 100 Myr), Columba ((is) approximately 30 Myr), Tucana-Horogium ((is) approximately 30 Myr), and TW Hydrae ((is) approximately 10 Myr), are sufficiently well-defined to constrain the ages of individual targets. Somewhat less than half of our targets are high-probability members of one of these MGs. For all of our targets, we combine proposed MG membership with other age indicators where available, including Ca ii HK emission, X-ray activity, and rotation period, to produce a posterior probability distribution of age. SEEDS observations discovered a substellar companion to one of our targets, kappa And, a late B star. We do not detect any other substellar companions, but do find seven new close binary systems, of which one still needs to be confirmed. A detailed analysis of the statistics of this sample, and of the companion mass constraints given our age probability distributions and exoplanet cooling models, will be presented in a forthcoming paper.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN21522 , Astrophysical Journal; 786; 1; 1
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  • 5
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    The Architecture of the LkCa 15 Transitional Disk Revealed by High-contrast Imaging (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: We present four new epochs of Ks-band images of the young pre-transitional disk around LkCa 15, and perform extensive forward modeling to derive the physical parameters of the disk. We find indications of strongly anisotropic scattering (Henyey-Greenstein g = 0.67+0.18 0.11) and a significantly tapered gap edge ('round wall'), but see no evidence that the inner disk, whose existence is predicted by the spectral energy distribution, shadows the outer regions of the disk visible in our images. We marginally confirm the existence of an offset between the disk center and the star along the line of nodes; however, the magnitude of this offset (x = 27+19 20 mas) is notably lower than that found in our earlier H-band images (Thalmann et al. 2010). Intriguingly, we also find, at high significance, an offset of y = 69+49 25 mas perpendicular to the line of nodes. If confirmed by future observations, this would imply a highly elliptical- or otherwise asymmetric-disk gap with an effective eccentricity of e 0.3. Such asymmetry would most likely be the result of dynamical sculpting by one or more unseen planets in the system. Finally, we find that the bright arc of scattered light we see in direct imaging observations originates from the near side of the disk, and appears brighter than the far side because of strong forward scattering.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN14797
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  • 6
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    The Architecture of the LkCa 15 Transitional Disk Revealed By High-Contrast Imaging (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: We present four new epochs of Ks-band images of the young pre-transitional disk around LkCa 15 and perform extensive forward modeling to derive the physical parameters of the disk. We find indications of strongly anisotropic scattering (Henyey-Greenstein g = 0.67 (+0.18/0.11)) and a significantly tapered gap edge ("round wall") but see no evidence that the inner disk, whose existence is predicted by the spectral energy distribution, shadows the outer regions of the disk visible in our images.We marginally confirm the existence of an offset between the disk center and the star along the line of nodes; however, the magnitude of this offset (x = 27 (+19/20) mas) is notably lower than that found in our earlier H-band images. Intriguingly, we also find an offset of y = 69 (+49/25) mas perpendicular to the line of nodes at high significance. If confirmed by future observations, this would imply a highly elliptical - or otherwise asymmetric - disk gap with an effective eccentricity of e 0.3. Such asymmetry would most likely be the result of dynamical sculpting by one or more unseen planets in the system. Finally, we find that the bright arc of scattered light we see in direct imaging observations originates from the near side of the disk and appears brighter than the far side because of strong forward scattering.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN16522 , Astronomy & Astrophysics; 566; A51
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  • 7
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    Search for Cosmic-Ray-Induced Gamma-Ray Emission in Galaxy Clusters (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Current theories predict relativistic hadronic particle populations in clusters of galaxies in addition to the already observed relativistic leptons. In these scenarios hadronic interactions give rise to neutral pions which decay into gamma rays that are potentially observable with the Large Area Telescope (LAT) on board the Fermi space telescope. We present a joint likelihood analysis searching for spatially extended gamma-ray emission at the locations of 50 galaxy clusters in four years of Fermi-LAT data under the assumption of the universal cosmic-ray (CR) model proposed by Pinzke & Pfrommer. We find an excess at a significance of 2.7 delta, which upon closer inspection, however, is correlated to individual excess emission toward three galaxy clusters: A400, A1367, and A3112. We discuss these cases in detail and conservatively attribute the emission to unmodeled background systems (for example, radio galaxies within the clusters).Through the combined analysis of 50 clusters, we exclude hadronic injection efficiencies in simple hadronic models above 21% and establish limits on the CR to thermal pressure ratio within the virial radius, R(sub 200), to be below 1.25%-1.4% depending on the morphological classification. In addition, we derive new limits on the gamma-ray flux from individual clusters in our sample.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN17192 , The Astrophysical Journal; 787; 1; 18
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  • 8
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    NuSTAR Observations of Heavily Obscured Quasars at z Is Approximately 0.5 (2014)
    In:  CASI
    Details
    Publication Date: 2019-08-26
    Description: We present NuSTAR hard X-ray observations of three Type 2 quasars at z approx. = 0.4-0.5, optically selected from the Sloan Digital Sky Survey. Although the quasars show evidence for being heavily obscured, Compton-thick systems on the basis of the 2-10 keV to [O(sub III)] luminosity ratio and multiwavelength diagnostics, their X-ray absorbing column densities (N(sub H)) are poorly known. In this analysis, (1) we study X-ray emission at greater than 10 keV, where X-rays from the central black hole are relatively unabsorbed, in order to better constrain N(sub H). (2) We further characterize the physical properties of the sources through broad-band near-UV to mid-IR spectral energy distribution analyses. One of the quasars is detected with NuSTAR at greater than 8 keV with a no-source probability of less than 0.1%, and its X-ray band ratio suggests near Compton-thick absorption with N(sub H) is approximately greater than 5 10(exp 23) cm(exp -2). The other two quasars are undetected, and have low X-ray to mid-IR luminosity ratios in both the low-energy (2-10 keV) and high-energy (10-40 keV) X-ray regimes that are consistent with extreme, Compton-thick absorption (N(sub H) is approximately greater than 10(exp 24) cm(exp 2)). We find that for quasars at z is approximately 0.5, NuSTAR provides a significant improvement compared to lower energy (less than 10 keV) Chandra and XMM-Newton observations alone, as higher column densities can now be directly constrained.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN21863 , The Astrophysical Journal; 785; 1; 17
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  • 9
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    Dust Production and Particle Acceleration in Supernova 1987A Revealed with ALMA (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Supernova (SN) explosions are crucial engines driving the evolution of galaxies by shock heating gas, increasing the metallicity, creating dust, and accelerating energetic particles. In 2012 we used the Atacama Large Millimeter/ Submillimeter Array to observe SN1987A, one of the best-observed supernovae since the invention of the telescope. We present spatially resolved images at 450 m, 870 m, 1.4 mm, and 2.8 mm, an important transition wavelength range. Longer wavelength emission is dominated by synchrotron radiation from shock-accelerated particles, shorter wavelengths by emission from the largest mass of dust measured in a supernova remnant (〉0.2 Solar Mass). For the first time we show unambiguously that this dust has formed in the inner ejecta (the cold remnants of the exploded star's core). The dust emission is concentrated at the center of the remnant, so the dust has not yet been affected by the shocks. If a significant fraction survives, and if SN 1987A is typical, supernovae are important cosmological dust producers.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN15487 , The Astrophysical Journal; 782; 1; L2
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  • 10
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    On Lunar Exospheric Column Densities and Solar Wind Access Beyond the Terminator from ROSAT Soft X-Ray Observations of Solar Wind Charge Exchange (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: We analyze the Rontgen satellite (ROSAT) position sensitive proportional counter soft X-ray image of the Moon taken on 29 June 1990 by examining the radial profile of the surface brightness in three wedges: two 19 deg wedges (one north and one south) 13-32 deg off the terminator toward the dark side and one wedge 38 deg wide centered on the antisolar direction. The radial profiles of both the north and the south wedges show significant limb brightening that is absent in the 38 deg wide antisolar wedge. An analysis of the soft X-ray intensity increase associated with the limb brightening shows that its magnitude is consistent with that expected due to solar wind charge exchange (SWCX) with the tenuous lunar atmosphere based on lunar exospheric models and hybrid simulation results of solar wind access beyond the terminator. Soft X-ray imaging thus can independently infer the total lunar limb column density including all species, a property that before now has not been measured, and provide a large-scale picture of the solar wind-lunar interaction. Because the SWCX signal appears to be dominated by exospheric species arising from solar wind implantation, this technique can also determine how the exosphere varies with solar wind conditions. Now, along with Mars, Venus, and Earth, the Moon represents another solar system body at which SWCX has been observed.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN21415 , Journal of Geophysical Research: Planets; 119; 7; 1459–1478
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