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  • Astronomy  (473)
  • 1995-1999  (473)
  • 1970-1974
  • 1999  (243)
  • 1997  (230)
  • 1
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    UV irradiation of polycyclic aromatic hydrocarbons in ices: production of alcohols, quinones, and ethers (1999)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1999-02-19
    Description: Polycyclic aromatic hydrocarbons (PAHs) in water ice were exposed to ultraviolet (UV) radiation under astrophysical conditions, and the products were analyzed by infrared spectroscopy and mass spectrometry. Peripheral carbon atoms were oxidized, producing aromatic alcohols, ketones, and ethers, and reduced, producing partially hydrogenated aromatic hydrocarbons, molecules that account for the interstellar 3.4-micrometer emission feature. These classes of compounds are all present in carbonaceous meteorites. Hydrogen and deuterium atoms exchange readily between the PAHs and the ice, which may explain the deuterium enrichments found in certain meteoritic molecules. This work has important implications for extraterrestrial organics in biogenesis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bernstein, M P -- Sandford, S A -- Allamandola, L J -- Gillette, J S -- Clemett, S J -- Zare, R N -- New York, N.Y. -- Science. 1999 Feb 19;283(5405):1135-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉NASA-Ames Research Center, Mail Stop 245-6, Moffett Field, CA 94035-1000, USA. mbernstein@mail.arc.nasa.gov〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10024233" target="_blank"〉PubMed〈/a〉
    Keywords: Alcohols/chemistry ; Astronomical Phenomena ; Astronomy ; Deuterium/chemistry ; Ethers/chemistry ; *Evolution, Chemical ; *Exobiology ; Hydrogen/chemistry ; *Ice ; Mass Spectrometry ; Meteoroids ; Origin of Life ; Oxidation-Reduction ; Photolysis ; Polycyclic Hydrocarbons, Aromatic/*chemistry ; Quinones/chemistry ; Spectrophotometry, Infrared ; *Ultraviolet Rays
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
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    A barely tested hypothesis (1999)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1999-12-28
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hogg, D W -- New York, N.Y. -- Science. 1999 Nov 26;286(5445):1679.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10610561" target="_blank"〉PubMed〈/a〉
    Keywords: Astronomical Phenomena ; Astronomy ; *Biological Evolution ; Selection, Genetic
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Molecules on a space odyssey (1999)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1999-03-13
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ehrenfreund, P -- New York, N.Y. -- Science. 1999 Feb 19;283(5405):1123-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Austrian Academy of Sciences and at Leiden Observatory, Leiden, The Netherlands. pascale@strw.leidenuniv.nl〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10075570" target="_blank"〉PubMed〈/a〉
    Keywords: Astronomical Phenomena ; Astronomy ; *Cosmic Dust ; Deuterium/chemistry ; Earth (Planet) ; *Evolution, Chemical ; *Exobiology ; Hydrogen/chemistry ; Ice ; Meteoroids ; Origin of Life ; Polycyclic Hydrocarbons, Aromatic/*chemistry ; Ultraviolet Rays
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Goddard Geophysical and Astronomical Observatory (1999)
    In:  CASI
    Details
    Publication Date: 2011-09-13
    Description: This report summarizes the technical parameters and the technical staff of the VLBI system at GGAO. It also gives an overview of VLBI activities during the previous year. The outlook lists the tasks planned for 1999.
    Keywords: Astronomy
    Type: International VLBI Service for Geodesy and Astrometry: 1999 Annual Report; 46-48; NASA/TP-1999-209243
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  • 5
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    The Next Generation Space Telescope (NGST): Science and technology (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The scientific requirements and implications for the instruments and telescope design for the Next Generation Space Telescope (NGST) are described. A candidate concept is a deployable, 8 m diameter telescope, optimized for the near infrared region, but featuring instruments capable of observing up to 30 micrometers. The observatory is radiatively cooled to approximately 30 K.
    Keywords: Astronomy
    Type: ; 213-218
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  • 6
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    Simulations of the STIS CCD clear imaging mode PSF (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Detailed understanding of the properties of the point-spread function (PSF) of Space Telescope Imaging Spectrograph (STIS) imaging modes is necessary to separate real effects of geometrically complex astronomical sources, such as protoplanetary disks surrounding bright stars, from instrumental effects, such as scattering and diffraction. In order to investigate STIS imaging properties we have numerically simulated broadband stellar PSFs generated by STIS in CCD clear imaging mode, including the effects of the Lyot stop and the coronagraphic wedges. The input spectrum is a stellar model atmosphere of the appropriate spectral type, convolved with the pre-flight STIS CCD response function. The PSF modeler generates broadband PSFs by co-adding weighted monochromatic PSFs across the waveband.
    Keywords: Astronomy
    Type: The 1997 HST Calibration Workshop with a New Generation of Instruments; 84-89; NASA/TM-97-208141
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  • 7
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    Correction for the STIS echelle blaze function (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Using the Early Release Observation of 9 Comae, we demonstrate an iterative method for correcting Space Telescope Imaging Spectrograph (STIS) echelle spectra for the effects of the echelle ripple. This analytic approach allows the actual spectrum of interest to be used in the determination of its calibration. The late F star 9 Comae is not an ideal candidate for this method, due to the many absorption lines present in its E230M spectrum, yet, given this difficulty, the method still works quite well.
    Keywords: Astronomy
    Type: The 1997 HST Calibration Workshop with a New Generation of Instruments; 114-119; NASA/TM-97-208141
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  • 8
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    The STIS parallel survey: Introduction and first results (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The installation of the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST) allows for the first time two-dimensional optical and ultraviolet slitless spectroscopy of faint objects from space. The STIS Parallel Survey (SPS) routinely obtains broad band images and slitless spectra of random fields in parallel with HST observations using other instruments. The SPS is designed to study a wide variety of astrophysical phenomena, including the rate of star formation in galaxies at intermediate to high redshift through the detection of emission-line galaxies. We present the first results of the SPS, which demonstrate the capability of STIS slitless spectroscopy to detect and identify high-redshift galaxies.
    Keywords: Astronomy
    Type: The 1997 HST Calibration Workshop with a New Generation of Instruments; 94-99; NASA/TM-97-208141
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  • 9
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    An investigation into the milliarcsecond attitude control errors of Hubble Space Telescope (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: An analysis of the fine pointing errors of the Hubble Space Telescope (HST), in the range from 1 to 15 milliarcsecs, is reported on. The emphasis is on the study of the performance characteristics of the pointing control system, fine guidance sensors and the optical telescope assembly, which produce relative attitude and astrometric measurement errors. Since the first servicing mission in December 1993, the HST relative short term position stability is of the order of 3 milliarcsecs RMS when averaged over 1 min intervals. At this level of accuracy, longer term systematic attitude errors in this range can have a noticeable impact on the telescope's observations. The various error sources are described, including: internal temperature effects; spacecraft structure temperature effects; calibration procedures, and computational inaccuracies.
    Keywords: Astronomy
    Type: ; 233-238
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  • 10
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    Global astrometry with the space interferometry mission (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The prospects for global astrometric measurements with the space interferometry mission (SIM) are discussed. The SIM mission will perform four microarcsec astrometric measurements on objects as faint as 20 mag using the optical interferometry technique with a 10 m baseline. The SIM satellite will perform narrow angle astrometry and global astrometry by means of an astrometric grid. The sensitivities of the SIM global astrometric performance and the grid accuracy versus instrumental parameters and sky coverage schemes are reported on. The problems in finding suitable astrometric grid objects to support microarcsec astrometry, and related ground-based observation programs are discussed.
    Keywords: Astronomy
    Type: ; 789-793
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  • 11
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    The scientific basis for the space interferometry mission (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The space interferometry mission (SIM), for launch in 2004, is expected to determine the positions of point sources to a global accuracy of 4 microarcsec, and an accuracy of 1 microarcsec over small angles. The instrument will reach 200 mag in 3 x 10(exp 4) s and has a nominal lifetime of five years. A nulling capability will be provided and synthesis imaging and near-infrared capabilities are being considered. These capabilities will extend those of the Hipparcos mission by almost three orders of magnitude in every sense. The NASA's expectation for the scientific return from the SIM mission is outlined in terms of the areas of stellar physics, galactic structure and extragalactic astrophysics, including the distance scale problem.
    Keywords: Astronomy
    Type: ; 749-753
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  • 12
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    High energy survey of supernova remnants with BATSE (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The burst and transient source experiment (BATSE) survey of the high energy emission from supernova remnants is reported on. The ability of BATSE to continuously monitor the entire sky in the 20 keV to 2 MeV energy range enables a large group of remnants to by studied at high energies. Preliminary analysis indicates the likely detection of several supernova remnants other than the Crab nebula. Among these are MSH 15-52, Vela, Cas A and possibly HB 9. The techniques employed are discussed together with the status of the survey and its limitations.
    Keywords: Astronomy
    Type: ; 547-550
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  • 13
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    High-resolution spectral measurements of GRO J1655-40 (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Data from the transient gamma ray germanium detector taken during 1995 provide a limited ability to study the high resolution spectrum of the X-ray transient GRO J1655-40. During a two-day period around the peak intensity, the soft spectrum was measured and found to be consistent with a power law spectrum with photon index -3.0 +/- 0.2. No evidence was found for narrow spectral features in the 50 to 100 keV band or around 511 keV. The 3 sigma upper limit for a narrow emission line at 511 keV is 1.2 x 10(exp -2) phot/cu cm s.
    Keywords: Astronomy
    Type: Proceedings of 2nd INTEGRAL Workshop 'The Transparent Universe'; 229-232; ESA-SP-382
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  • 14
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    STIS target acquisition (1997)
    In:  CASI
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    Publication Date: 2004-12-03
    Description: We describe the STIS autonomous target acquisition capabilities. We also present the results of dedicated tests executed as part of Cycle 7 calibration, following post-launch improvements to the Space Telescope Imaging Spectrograph (STIS) flight software. The residual pointing error from the acquisitions are 〈 0.5 CCD pixels, which is better than preflight estimates. Execution of peakups show clear improvement of target centering for slits of width 0.1 sec or smaller. These results may be used by Guest Observers in planning target acquisitions for their STIS programs.
    Keywords: Astronomy
    Type: The 1997 HST Calibration Workshop with a New Generation of Instruments; 39-46; NASA/TM-97-208141
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  • 15
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    Thermal motion of the STIS optical bench (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Various tests have been done of the Space Telescope Imaging Spectrograph (STIS) using internal wavecals to measure thermal motion of the spectral format on the detectors. In most cases, the spectral format moves less than the specification not to exceed 0.2 pixels per hour. Primary causes of the motion are (1) changes to the thermal design dictated by the warmer Aft Shroud environment and (2) on-orbit power cycling of Multi-Anode Microchannel Arrays (MAMA) electronics to minimize the effects of radiation hits on the MAMA detectors. The rear portion of the STIS optical bench is too warm to be held at a constant temperature by internal heaters. Electronics swing in temperature with an orbital and daily frequency. The thermal drift of the optical formats is not negligible, but is well behaved in most circumstances. The observer is advised to examine the trade-off between the most accurate wavelengths with best spectral/spatial resolutions versus increased overheads that directly affect the observing times. A long term concern is that the Aft Shroud thermal environment is predicted to heat up as much as one Centigrade degree per year. Progressively more of the bench would move out of thermal control. Thus the external cooler for STIS, being considered for the Third Servicing Mission is of major importance to the long term operation of STIS.
    Keywords: Astronomy
    Type: The 1997 HST Calibration Workshop with a New Generation of Instruments; 106-113; NASA/TM-97-208141
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  • 16
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    Implications of the broad Al-26 1809 keV line observed by GRIS (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The astrophysical implications of the large width of the 1809 keV gamma ray line from the decay of radioactive Al-26, recently observed with the gamma ray imaging spectrometer (GRIS), are discussed. While there may be no apparent single mechanism that can explain the observed broadening, high speed dust grains, extremely hot superbubbles and a large, low density gaseous halo were identified in the Galactic center region as the possible origins. The implications of these observations on the hot gas content in the interstellar medium are discussed.
    Keywords: Astronomy
    Type: ; 105-108
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  • 17
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    Issues concerning the Orion gamma ray line observations: Line splitting and LiBeB origin (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The phenomenon of broad gamma ray line splitting is discussed, together with a scenario for the suppression of the blue wings of these broad lines due to the geometry of the accelerated particle interaction region. The broad and narrow gamma ray line emissions are compared taking into account the line splitting effect. It is concluded that the observed gamma ray lines from Orion are most likely broad, implying that the low energy cosmic rays which produce this line emission consist mostly of C and heavier ions. The suppression of the proton and alpha particle abundances requires acceleration conditions such as the acceleration of the ejecta of the supernovae before mixing with the interstellar medium. Similar conditions are implied by observations of the B and Be in low metallicity stars formed during the first Gyr of galactic evolution.
    Keywords: Astronomy
    Type: Proceedings of 2nd INTEGRAL Workshop 'The Transparent Universe'; 75-78; ESA-SP-382
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  • 18
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    An Alternative Lunar Ephemeris Model for On-Board Flight Software Use (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: In calculating the position vector of the Moon in on-board flight software, one often begins by using a series expansion to calculate the ecliptic latitude and longitude of the Moon, referred to the mean ecliptic and equinox of date. One then performs a reduction for precession, followed by a rotation of the position vector from the ecliptic plane to the equator, and a transformation from spherical to Cartesian coordinates before finally arriving at the desired result: equatorial J2000 Cartesian components of the lunar position vector. An alternative method is developed here in which the equatorial J2000 Cartesian components of the lunar position vector are calculated directly by a series expansion, saving valuable onboard computer resources.
    Keywords: Astronomy
    Type: 1999 Flight Mechanics Symposium; 175-184; NASA/CP-1999-209235
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  • 19
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    BATSE as an all-sky monitor for INTEGRAL (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: It is proposed to use data from the burst and transient source experiment (BATSE) onboard the Compton Gamma Ray Observatory (CGRO) as a sensitive, rapid, all sky monitor for the International Gamma Ray Astrophysics Laboratory (INTEGRAL). The all sky earth occultation monitoring and imaging capabilities of BATSE will complement and extend the Galactic plane scans of INTEGRAL as well as provide high latitude Galactic coverage which is inaccessible to INTEGRAL. Examples of transients previously observed by BATSE, its sensitivity, and the response time for these observations are described. Examples of the variability of several of the brighter sources observed by BATSE are shown.
    Keywords: Astronomy
    Type: Proceedings of 2nd INTEGRAL Workshop 'The Transparent Universe'; 537-540; ESA-SP-382
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  • 20
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    Observing gamma-ray bursts with the INTEGRAL spectrometer SPI (1997)
    In:  CASI
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    Publication Date: 2004-12-03
    Description: The spectrometer for INTEGRAL (SPI) is a germanium spectrometer with a wide field of view and will provide the International Gamma Ray Astrophysics Laboratory (INTEGRAL) mission with the opportunity of studying gamma ray bursts. Simulations carried out to assess the response of the instrument using data from real burst data as input are reported on. It is shown that, despite the angular resolution of 3 deg, it is possible to locate the direction of bursts with an accuracy of a few arcmin, while offering the high spectral resolution of the germanium detectors. It is remarked that the SPI field of view is similar to the size of the halo of bursts expected around M 31 on galactic models. The detectability of bursts with such a halo is discussed.
    Keywords: Astronomy
    Type: ; 487-490
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  • 21
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    Gamma-ray observations of BL Lac objects (1997)
    In:  CASI
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    Publication Date: 2004-12-03
    Description: The results from observations of a sample of BL Lac objects by the Compton telescope (COMPTEL) and energetic gamma ray experiment telescope (EGRET) onboard the Compton Gamma Ray Observatory (CGRO) are presented. The main targets in the sample were selected on the basis of their X-ray brightness and apparent spectral hardening at hard X-ray energies. One of the targets, PKS 0521-365 was detected by EGRET, and these data are presented together with contemporaneous ground-based radio data. Subsequent X-ray observations of this source with the Advanced Satellite for Cosomology and Astrophysics (ASCA) demonstrated that, although originally classified as a BL Lac object, it is better described as a flat spectrum radio quasar. Upper limits on the gamma ray flux from all the non-detected BL lacs are presented.
    Keywords: Astronomy
    Type: ; 413-416
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  • 22
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    Radio and X-ray observations of GX 339-4 (1997)
    In:  CASI
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    Publication Date: 2004-12-03
    Description: Observations of the Galactic black hole candidate binary system GX 339-4 at radio, optical and X-ray wavelengths are reviewed. The radio observations reveal a compact, persistent and variable source. On the average, the radio intensity is less than 10 mJy. These data, when compared with previous data, indicate no set correlation between the radio and X-ray emission. The X-ray intensity suggests a 14.5 month cycle. The latest radio observational data are presented together with X-ray data and are discussed in the context of similar correlated observations from other X-ray binaries.
    Keywords: Astronomy
    Type: Proceedings of 2nd INTEGRAL Workshop 'The Transparent Universe'; 201-204; ESA-SP-382
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  • 23
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    Hard X-ray spectra of neutron stars and black hole candidates (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The hard X-ray behavior of several X-ray binary systems containing a neutron star or a black hole candidate is analyzed in an attempt to determine the specific signature of these categories of compact objects. Limiting the consideration to two subclasses of neutron stars, Atoll sources and non-pulsating Z sources, it appears that only the Atoll sources have a spectral behavior similar to black holes. It is proposed that Atoll sources are weakly magnetized neutron stars, whereas Z sources are small radius moderate magnetized neutron stars. Large magnetic fields funnel the accreting matter, thus preventing spherical accretion and free fall if the neutron star radius is smaller than the last stable accreting orbit. Weak magnetic fields do not have this effect, and blackbody soft photons from the stellar surface are upscattered on the relativistic infalling matter, leading to excess hard X-rays. This excess is visible in two of the observed Atoll sources and in the spectrum of a black hole candidate. In the case of a Z source, a lack of photons was remarked, providing a possible signature to distinguish between these classes of objects.
    Keywords: Astronomy
    Type: Proceedings of 2nd INTEGRAL Workshop 'The Transparent Universe'; 137-139; ESA-SP-382
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  • 24
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    The Submillimeter Wave Astronomy Satellite: Science objectives and instrument description (1997)
    In:  CASI
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    Publication Date: 2004-12-03
    Description: The submillimeter wave astronomy satellite (SWAS) mission is dedicated to the investigation of star formation and interstellar chemistry. In order to perform the mission, SWAS will survey dense molecular clouds within the Milky Way Galaxy in either the ground state or a low-lying transition of five astrophysically-significant species: H2O, H2(18)O, O2, C I and (13)CO. The observation of these lines will: test theories that predict that these species are dominant coolants of molecular clouds during early stages of their collapse to form stars and planets, and supply information concerning the abundance of species central to the chemical models of dense interstellar gas. The SWAS will use two independent Schottky barrier diode mixers and a 53 x 68 sq cm, off-axis Cassegrain antenna.
    Keywords: Astronomy
    Type: ; 189-194
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  • 25
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    The "Water-Fountain Nebula" IRAS 16342-3814: Hubble Space Telescope/Very Large Array Study of a Bipolar Protoplanetary Nebula (1999)
    In:  Other Sources
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    Publication Date: 2011-08-23
    Description: We present Hubble Space Telescope (HST) Wide-Field Planetary Camera 2 images and VLA OH maser emission-line maps of the cold infrared object IRAS 16342-3814, believed to be a protoplanetary nebula. The HST images show an asymmetrical bipolar nebula, with the lobes separated by a dark equatorial waist. The two bright lobes and the dark waist are simply interpreted as bubble-like reflection nebulae illuminated by starlight escaping through polar holes in a dense, flattened, optically thick cocoon of dust, which completely obscures the central star. A faint halo can be seen surrounding each of the lobes. The bubbles are likely to have been created by a fast outflow (evidenced by H2O emission) plowing into a surrounding dense, more slowly expanding, circumstellar envelope of the progenitor asymptotic giant-branch (AGB) star (evidenced by the halo). The IRAS fluxes indicate a circumstellar mass of about 0.7 solar mass (D/2 kpc) and an AGB mass-loss rate of about 10(exp -4) solar mass/yr (V(sub exp)/15 km/s)(D/2 kpc)(sup 2) (assuming a gas-to-dust ratio of 200). OH features with the largest redshifted and blueshifted velocities are concentrated around the bright eastern and western polar lobes, respectively, whereas intermediate-velocity features generally occur at low latitudes, in the dark waist region. We critically examine evidence for the post-AGB classification of IRAS 16342-3814.
    Keywords: Astronomy
    Type: Astrophysical Journal; No. 2
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  • 26
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    Comets: Very Eccentric Characters (1999)
    In:  Other Sources
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    Publication Date: 2011-08-23
    Description: Astronomical distances, even within our own solar system, are very difficult for anyone, let alone children, to imagine. In this month's space-program-related activity, students have the opportunity to create a visual and kinesthetic model of the solar system on a scale that may begin to inspire an awed comprehension of how big space is and how small Earth is. In addition, they will learn a little basic geometry in demonstrating for themselves the difference between a circular planetary orbit and an elongated elliptical cometary orbit. As a space exploration first the Jet Propulsion Laboratory (JPL), under contract to the National Aeronautics and Space Administration (NASA), is planning to send a spacecraft to rendezvous with and land on a comet. The Space Technology 4/Champollion mission is part of NASA's New Millennium Program, the primary goal of which is to test new technologies for use in 21st century planetary and earth observing missions.
    Keywords: Astronomy
    Type: The Technology Teacher: The Voice of Technology Education; Volume 58; No. 7
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  • 27
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    On the Dramatic Spin-up/Spin-Down Torque Reversals in Accreting Pulsars (1997)
    In:  Other Sources
    Details
    Publication Date: 2011-08-23
    Description: Dramatic torque reversals between spin-up and spin-down have been observed in half of the persistent X-ray pulsars monitored by the Burst and Transient Space Experiment (BATSE) all-sky monitor on the Compton Gamma Ray Observatory. Theoretical models developed to explain early pulsar timing data can explain spin-down torques via a disk-magnetosphere interaction if the star nearly corotates with the inner accretion disk. To produce the observed BATSE torque reversals, however, these equilibrium models require the disk to alternate between two mass accretion rates, with M+/- producing accretion torques of similar magnitude but always of opposite sign. Moreover, in at least one pulsar (GX 1+4) undergoing secular spin-down, the neutron star spins down faster during brief (approximately 20 day) hard X-ray flares-this is opposite the correlation expected from standard theory, assuming that BATSE pulsed flux increases with mass accretion rate. The 10 day to 10 yr intervals between torque reversals in these systems are much longer than any characteristic magnetic or viscous timescale near the inner disk boundary and are more suggestive of a global disk phenomenon. We discuss possible explanations of the observed torque behavior. Despite the preferred sense of rotation defined by the binary orbit, the BATSE observations are surprisingly consistent with an earlier suggestion for GX 1+4: the disks in these systems somehow alternate between episodes of prograde and retrograde rotation. We are unaware of any mechanism that could produce a stable retrograde disk in a binary undergoing Roche lobe overflow, but such flip-flop behavior does occur in numerical simulations of wind-fed systems. One possibility is that the disks in some of these binaries are fed by an X-ray-excited wind.
    Keywords: Astronomy
    Type: Astrophysical Journal; Volume 488; L117-L120
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  • 28
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    The High Throughput X-ray Spectroscopy (HTXS) Mission (1997)
    In:  Other Sources
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    Publication Date: 2011-08-23
    Description: The HTXS mission concept combines large effective area (approximately 15,000 sq cm at 1 keV), high spectral resolution (E/Delta(E) approximately 300-3000), and broad energy bandpass (0.25-40 keV and possibly up to 100 keV) by using replicated optics together with a complement of spectroscopic instrumentation including reflection gratings readout by charge-coupled device detectors (CCDs), quantum micro-calorimeters, and cadmium zinc telluride (CZT) or comparable high energy detectors. An essential feature of this concept involves minimization of cost (approximately $350M for development and approximately $500-600M including launches) and risk by building six identical modest satellites to achieve the large area. Current mission and technology studies are targeted towards a new start in the 2002 timeframe, with first launch around 2005-2006. The HTXS mission represents a major advance, providing as much as a factor of 100 increase in sensitivity over currently planned high resolution X ray spectroscopy missions. HTXS will mark the start of a new era when high quality X ray spectra will be obtained for all classes of X ray sources, over a wide range of luminosity and distance. With its increased capabilities, HTXS will address many fundamental astrophysics questions such as the origin and distribution of the elements from carbon to zinc, the formation and evolution of clusters of galaxies, the validity of general relativity in the strong gravity limit, the evolution of supermassive black holes in active galactic nuclei, the details of supernova explosions and their aftermath, and the mechanisms involved in the heating of stellar coronae and driving of stellar winds.
    Keywords: Astronomy
    Type: The Next Generation of X-Ray Observatories; 173-189; XRA97/02
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    The Progenitor of the New COMPTEL/ROSAT Supernova Remnant in Vela (1999)
    In:  Other Sources
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    Publication Date: 2011-08-23
    Description: We show that (1) the newly discovered supernova remnant (SNR) GROJ0852-4642/RXJ0852.0-4622 was created by a core-collapse supernova of a massive star and (2) the same supernova event that produced the Ti-44 detected by COMPTEL from this source is probably also responsible for a large fraction of the observed Al-26 emission in the Vela region detected by the same instrument. The first conclusion is based on the fact that the remnant is currently expanding too slowly given its young age for it to be caused by a Type la supernova. If the current SNR shell expansion speed is greater than 3000 km/s, a 15 solar mass. Type II supernova with a moderate kinetic energy exploding at about 150 pc away is favored. If the SNR expansion speed is lower than 2000 km/s, as derived naively from X-ray data, a much more energetic supernova is required to have occurred at approximately 250 pc away in a dense environment at the edge of the Gum Nebula. This progenitor has a preferred ejecta mass of less than or equal to 10(Solar Mass), and therefore it is probably a Type Ib or Type Ic supernova. However, the required high ambient density of n(sub H) greater than or equal to 100 cu cm in this scenario is difficult to reconcile with the regional CO data. A combination of our estimates of the age/energetics of the new SNR and the almost perfect positional coincidence of the new SNR with the centroid of the COMPTEL Al-26 emission feature of the Vela region strongly favors a causal connection. If confirmed, this will be the first case in which both Ti-44 and Al-26 are detected from the same young SNR, and together they can be used to select preferred theoretical core-collapse supernova models.
    Keywords: Astronomy
    Type: Astrophysical Journal; Volume 514; 1-4
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  • 30
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    A Correlation Between Length of Strong-Shear Neutral Lines and Total X-Ray Brightness in Active Regions (1997)
    In:  Other Sources
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    Publication Date: 2011-08-23
    Description: From a sample of 7 MSFC vector magnetograms,of active regions and 17 Yohkoh SXT soft X-ray images of these active regions, we have found that the total x-ray brightness of an entire active region is correlated with the total length of neutral lines on which the magnetic field is both strong (less than 250 G) and strongly sheared (shear angle greater than 75 deg) in the same active region. This correlation, if not fortuitous, is additional evidence of the importance of strong-shear strong-field neutral lines to strong heating in active regions.
    Keywords: Astronomy
    Type: Solar Physics; Volume 176; 123-126
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  • 31
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    Prospects for the Next Generation of X-ray Astronomy (1997)
    In:  Other Sources
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    Publication Date: 2011-08-23
    Description: This rapporteur contribution attempts to summarize the discussions at this conference in the context of current funding realities.
    Keywords: Astronomy
    Type: The Next Generation of X-Ray Observatories; 221-226; XRA97/02
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  • 32
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    The Astro -E/XRS Calibration Program and Results (1999)
    In:  Other Sources
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    Publication Date: 2011-08-23
    Description: XRS is the microcalorimeter X-ray detector aboard the US-Japanese ASTRO-E observatory, which is scheduled to be launched in early 2000. XRS is a high resolution spectrometer- with less than 9 eV resolution at 3 keV and better than 14 eV resolution over its bandpass ranging from about 0.3 keV to 15 keV. Here we present the results of our first calibration of the XRS instrument. We describe the methods used to extract detailed information about the detection efficiency and spectral redistribution of the instrument. We also present comparisons of simulations and real data to test our detector models
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  • 33
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    The Low-Mass X-Ray Binary X1832-330 in the Globular Cluster NGC 6652: A Serendipitous ASCA Observation (1999)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The Low Mass X-ray Binary (LMXB) X1832-330 in NGC 6652 is one of about 10 bright X-ray sources to have been discovered in Globular Clusters. We report on a serendipitous ASCA observation of this Globular Cluster LMXB, during which a Type I burst was detected and the persistent, non-burst emission of the source was at its brightest level recorded to date. No orbital modulation was detected, which argues against a high inclination for the X1832-330 system. The spectrum of the persistent emission can be fit with a power law plus a partial covering absorber, although other models are not ruled out. Our time-resolved spectral analysis through the burst shows, for the first time, clear evidence for spectral cooling from kT = 2.4 +/- 0.6 keV to kT = 1.0 +/- 0.1 keV during the decay. The measured peak flux during the burst is approximately 10% of the Eddington luminosity for a 1.4 Solar Mass neutron star. These are characteristic of a Type I burst, in the context of the relatively low quiescent luminosity of X1832-330.
    Keywords: Astronomy
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    Direct Measurement of the Supernova Rate in Starburst Galaxies (1999)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: Supernovae play a key role in the dynamics, structure, and chemical evolution of galaxies. The massive stars that end their lives as supernovae live for short times. Many are still associated with dusty star formation regions when they explode, making them difficult to observe at visible wavelengths. In active star forming regions (galactic nuclei and starburst regions), dust extintion is especially severe. Thus, determining the supernova rate in the active star forming regions of galaxies, where the supernova rate can be one or two orders of magnitude higher than the average, has proven to be difficult. From observations of SN1987A, we know that the [NiII] 6.63 micron emission line was the strongest line in the infrared spectrum for a period of a year and a half after the explosion. Since dust extintion is much less at 6.63 pm than at visible wavelengths (A(sub 6.63)/A(sub V) = 0.025), the NiII line can be used as a sensitive probe for the detection of recent supernovae. We have observed a sample of starburst galaxies at 6.63 micron using ISOCAM to search for the NiII emission line characteristic of recent supernovae. We did not detect any NiII line emission brighter than a 5sigma limit of 5 mJy. We can set upper limits to the supernova rate in our sample, scaled to the rate in M82, of less than 0.3 per year at the 90% confidence level using Bayesian methods. Assuming that a supernova would have a NiII with the same luminosity as observed in SN1987A, we find less than 0.09 and 0.15 per year at the 50% and 67% confidence levels. These rates are somewhat less if a more normal type II supernovae has a NiII line luminosity greater than the line in SN1987A.
    Keywords: Astronomy
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  • 35
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    A Catalog of Soft X-Ray Shadows, and More Contemplation of the 1/4 KeV Background (1999)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: This paper presents a catalog of shadows in the 1/4 keV soft X-ray diffuse background 4 (SXRB) that were identified by a comparison between ROSAT All-Sky Survey maps and DIRB&corrected IRAS 100 micron maps. These "shadows" are the negative correlations between the surface brightness of the SXRB and the column density of the Galactic interstellar medium (ISIM) over limited angular regions (a few degrees in extent). We have compiled an extensive but not exhaustive set of 378 shadows in the polar regions of the Galaxy (Absolute value (beta) 〉 and approximately equal 20 deg.), and determined their foreground and background X-ray intensities (relative to the absorbing features), and the respective hardness ratios of that emission. The portion of the sky that was examined to find these shadows was restricted in general to regions where the minimum column density is less than and approximately equal to 4 x 10(exp 20) H/square cm, i.e., relatively high Galactic latitudes, and to regions away from distinct extended features in the SXRB such as supernova remnants and superbubbles. The results for the foreground intensities agree well with the recent results of a general analysis of the local 1/4 KeV emission while the background intensities show additional. but not unexpected scatter. The results also confirm the existence of a gradient in the hardness of the local 1/4 keV emission along a Galactic center/ anticenter axis with a temperature that varies from 10(exp 6.13) K to 10(exp 6.02) K, respectively. The average temperature of the foreground component from this analysis is 10(exp 6.08) K, compared to 10(exp 6.06) K in the previous analysis. Likewise, the average temperature for the distant component for the current and previous analyses are 10(exp 6.06) K and 10(exp 6.02) K, respectively. Finally, the results for the 1/4 keV halo emission are compared to the observed fluxes at 3/4 keV, where the lack of correlation suggests that the Galactic halo's 1/4 keV and 3/4 keV fluxes are likely produced by separate emission regions.
    Keywords: Astronomy
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  • 36
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    ASCA Observation of the Dipping X-Ray Source X1916-053 (1997)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: We present the results of timing and spectral studies of the dipping X-ray source X1916-053, observed by ASCA during its Performance Verification phase. The detected dipping activity is consistent with previous observations, with a period of 3008s and an intermittent secondary dip observed roughly 0.4 out of phase with the primary dip. The energy spectra of different intensity states are fitted with a power law with partial covering fraction absorption and interstellar absorption. The increase in the hardness ratio during the primary and secondary dips, and the increase in the covering fraction and column density with decreasing X-ray intensity, all imply that the dipping is caused by the photo-absorbing materials which have been suggested to be where the accreted flow hits the outer edge of the disk materials. The spectra at all intensity levels show no apparent evidence for Fe or Ne emission lines. This may be due to the low metal abundance in the accretion flow. Alternatively, the X-ray luminosity of the central source may be too weak to excite emission lines, which are assumed to be produced by X-ray photoionization of the disk materials.
    Keywords: Astronomy
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  • 37
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    Photometric Observations of 6000 Stars in the Cygnus Field (1999)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: A small photometer to detect transits by extrasolar planets has been assembled and is being tested at Lick Observatory on Mt. Hamilton, California. The Vulcan photometer is constructed from a 30 cm focal length, F/2.5 AeroEktar reconnaissance lens and Photometrics PXL16800 CCD camera. A spectral filter is used to confine the pass band from 480 to 763 mn. It simultaneously monitors 6000 stars brighter than 12th magnitude within a single star field in the galactic plane. When the data are folded and phased to discover low amplitude transits, the relative precision of one-hour samples is about 1 part per thousand (10 x l0(exp -3)) for many of the brighter stars. This precision is sufficient to find jovian-size planets orbiting solar-like stars, which have signal amplitudes from 5 to 30 x l0(exp -3) depending on the inflation of the planet and the size of the star. Based on the frequency of giant inner-planets discovered by Doppler-velocity method, one or two planets should be detectable in a rich star field. The goal of the observations is to obtain the sizes of giant extrasolar planets in short-period orbits and to combine these with masses determined from Doppler velocity measurements to determine the densities of these planets. A further goal is to compare the measured planetary diameters with those predicted from theoretical models. From August 10 through September 30 of 1998, a forty nine square degree field in the Cygnus constellation centered at RA and DEC of 19 hr 47 min, +36 deg 55 min was observed. Useful data were obtained on twenty-nine nights. Nearly fifty stars showed some evidence of transits with periods between 0.3 and 8 days. Most had amplitudes too large to be associated with planetary transits. However, several stars showed low amplitude transits. The data for several transits of each of these two stars have been folded and been folded into 30 minute periods. Only Cygl433 shows any evidence of a flattened bottom that is expected when a small object transits a much larger primary. However when high-resolution spectra were obtained for both stars, the stars were found to be double-lined binaries so similar in size as to have indistinguishable transit depths. The low amplitude of the transits is explained if the stellar orbital planes are tipped approximately 5 degrees from the line of sight causing both binaries to show grazing transits. The two absorption lines, due to the H(sub beta) feature in each star, are apparent and indicate the presence of a binary system with similar components.
    Keywords: Astronomy
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  • 38
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    A Highly Doppler Blueshifted Fe-K Emission Line in the High-Redshift QSO PKS 2149-306 (1999)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: We report the results from an ASCA observation of the high-luminosity, radioloud quasar PKS 2149-306 (redshift 2.345), covering the approximately 1.7 - 30 keV band in the quasar-frame. We find the source to have a luminosity of approximately 6 x 10(exp 47) ergs/s in the 2 - 10 keV band (quasar frame). We detect an emission line centered at approximately 17 keV in the quasar frame. Line emission at this energy has not been observed in any other active galaxy or quasar to date. We present evidence rejecting the possibility that this line is the result of instrumental artifacts, or a serendipitous source. The most likely explanation is blueshifted Fe-K emission (the equivalent width, is EW approximately 300 +/- 200 eV, quasar frame). Bulk velocities of the order of 0.75c are implied by the data. We show that Fe-K line photons originating in an accretion disk and Compton-scattering off a leptonic jet aligned along the disk axis can account for the emission line. Curiously. if the emission-line feature recently discovered in another quasar (PKS 0637-752, z = 0.654) at 1.6 keV in the quasar frame, is due to blueshifted OVII emission, the Doppler blueshifting factor in both quasars is similar (approximately 2.7 - 2.8).
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  • 39
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    Near-Simultaneous Spectroscopic and Broadband Polarimetric Observations of Be Stars (1999)
    In:  Other Sources
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    Publication Date: 2011-08-23
    Description: Near simultaneous optical spectroscopic (on four nights) and broadband linear continuum (B, V, R, and I bands) polarimetric (on seven nights) observations of 29 Be stars were carried out during 1993 November-December. The program Be stars displayed wavelength dependence of intrinsic polarizations with no frequency dependence of polarimetric position angles. Some of the Be stars displayed long-term polarization variability. The Be and Be-shell stars could not be distinguished from one another solely on the basis of their polarization values. Full widths at half-maximum of the H.alpha profiles and the intrinsic linear continuum polarizations are closely correlated with the projected rotational velocities of the program stars. Photospheric-absorption-corrected equivalent widths of H.alpha profiles [W(alpha)] and the radii of H.alpha-emitting or -absorbing envelopes (R(sub e) or R(sub a)) are nonlinearly correlated with the intrinsic continuum polarizations of these stars. However, W(alpha) and R(sub e) are linearly correlated. With large uncertainties, there is a trend of spectral dependence of polarization. Detailed discussion of these results is presented in this paper.
    Keywords: Astronomy
    Type: Astronomical Journal; Volume 118; 1061-1072
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  • 40
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    Bright Points and Subflares in Ultraviolet Lines and X-Rays (1999)
    In:  Other Sources
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    Publication Date: 2011-08-23
    Description: We have analyzed an active region which was observed in H.alpha (Multichannel Subtractive Double Pass Spectrograph), in UV lines (SMM/UVSP), and in X-rays (SMM/HXIS). In this active region there were only a few subflares and many small bright points visible in UV and in X-rays. Using an extrapolation based on the Fourier transform, we have computed magnetic field lines connecting different photospheric magnetic polarities from ground-based magnetograms. Along the magnetic inversion lines we find two different zones: (1) a high-shear region (〉 70 deg) where subflares occur, and (2) a low-shear region along the magnetic inversion line where UV bright points are observed. In these latter regions the magnetic topology is complex with a mixture of polarities. According to the velocity field observed in the Si IV lamda.1402 line and the extrapolation of the magnetic field, we notice that each UV bright point is consistent with emission from low-rising loops with downflows at both ends. We notice some hard X-ray emissions above the bright-point regions with temperatures up to 8 x 10(exp 6) K, which suggests some induced reconnection due to continuous emergence of new flux. This reconnection is also enhanced by neighboring subflares.
    Keywords: Astronomy
    Type: Astrophysical Journal; Volume 510; 474-484
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    An Unusual Supernova in the Error Box of the Gamma-Ray Burst of 25 April 1998 (1999)
    In:  Other Sources
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    Publication Date: 2011-08-23
    Description: The discovery of afterglows associated with gamma-ray bursts at X-ray, optical and radio wavelengths and the measurement of the redshifts of some of these events has established that gamma-ray bursts lie at extreme distances, making them the most powerful photon-emitters known in the Universe. Here we report the discovery of transient optical emission in the error box of the gamma-ray burst GRB980425, the light curve of which was very different from that of previous optical afterglows associated with gamma-ray bursts. The optical transient is located in a spiral arm of the galaxy ESO 184-GS2, which has a redshift velocity of only 2,550 km/ s. Its optical spectrum and location indicate that it is a very luminous supernova, which has been identified as SN1998bw. If this supernova and GRB980425 are indeed associated, the energy radiated in gamma-rays is at least four orders of magnitude less than in other gamma-ray bursts, although its appearance was otherwise unremarkable: this indicates that very different mechanisms can give rise to gamma-ray bursts. But independent of this association, the supernova is itself unusual, exhibiting an unusual light curve at radio wavelengths that requires that the gas emitting the radio photons be expanding relativistically.
    Keywords: Astronomy
    Type: Nature; Volume 395; 670-672
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  • 42
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    Probing Europa's Hidden Ocean from Tidal Effects on Orbital Dynamics (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Division for Planetary Sciences Meeting of the American Astronomical Society; Padua; Italy
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    Sulfuric Acid on Europa's Surface and the Radiolytic Sulfur Cycle (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: Galileo infrared spectra of Europa's surface show distorted water bands that have been attributed to hydrated evaporite salts (McCord et al., J. Geophys. Res. 104, 11827, 1999) or to the scattering properties of ice (Dalton and Clark, Bull. Am. Astron. Soc. 30, 1081, 1998).
    Keywords: Astronomy
    Type: Division for Planetary Sciences Meeting of the American Astronomical Society; Padua; Italy
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    The Gravity Field and Interior Structure of Callisto (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Division for Planetary Sciences Meeting of the American Astronomical Society; Padua; Italy
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  • 45
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    Towards an Understanding of the Mid-Infrared Surface Brightness of Normal Galaxies (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We report a mid-infrared color and surface brightness analysis of IC 10, NGC 1313, and NGC 6946, three of the nearby galaxies studied under the Infrared Space Observatory Key Project on Normal Galaxies.
    Keywords: Astronomy
    Type: Astronomical Journal
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    The Etched Hourglass Nebula MyCn18: I. Hubble Space Telescope (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Astronomical Journal
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  • 47
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    Markarian 421's Unusual Satellite Galaxy (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We present Hubble Space Telescope (HST) imagery, and ground-based spectroscopy and CCD photometry of the active galaxy Markarian 421 and its companion galaxy 14 arcsec to the ENE.
    Keywords: Astronomy
    Type: Astronomical Journal
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  • 48
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    HST/NICMOS Imaging of Disks and Envelopes Around Very Young Stars (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We present HST/NICMOS observations with ~ 0''.1 = 15 AU resolution of six young stellar objects in the Taurus star-formation region.
    Keywords: Astronomy
    Type: Astronomical Journal
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  • 49
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    Coronal Hole Myth (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: AAS, Bulletin of American Astronomical Society; Chicago, IL; United States
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  • 50
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    Near/Mid Infrared-Wavelength Study of the Interacting Galaxy Pair UGC 12914/5 -- Taffy (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: The system consists of two counter-rotating spirals having suffered a nearly face-on collsion only ~10(sup 7) years ago.
    Keywords: Astronomy
    Type: Astronomical Journal
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    Astrometric Detection of a Low Mass Companion Orbiting the Star AB Doradus (1997)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We report submilliarsecond-precise astrometric measurement for the late-type star AB Doradus via a combination of VLBI (very long baseline interferometry) and Hipparos satellite data. Our astrometric analysis results in the precise determination of the kinematics of this star, that reveals an orbital motion readily explained as caused by the gravitational interaction with a low-mass companion.
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    The Dark Side of Iapetus and Hyperion: One and the Same? (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Division for Planetary Sciences Meeting of the American Astronomical Society; Padova; Italy
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    C II 158 ??bservations of a Sample of Late-type Galaxies from the Virgo Cluster (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We have observed 19 Virgo cluster spiral galaxies with the Long Wavelength Spectrometer (LWS) onboard ESAs Infrared Space Observatory (ISO) obtaining spectra around the [CII] 157.741 ??ine structure line.
    Keywords: Astronomy
    Type: Monthly Notices of the Royal Astronomical Society
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    A New Estimate of Hubble's Constant From The Gravitational Lens PKS 1830-211 (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: American Astronomical Society - Astronomy; Austin, TX; United States
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    Ground and Space-based Optical & IR Stellar Interferometry (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Japan National Astronomical Observatory; Tokyo; Japan
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    The Etched Hourglass Nebula MyCn18: II A Spatio-Kinematic Model (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We have observed MyCn18, a young Planetary Nebulae with HST/WFPC2 and presented the observational results in an earlier paper. Here we present a detailed spatial/kinematical model of H alpha emission from the nebula.
    Keywords: Astronomy
    Type: Astronomical Journal
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    The Astronomical Low Frequency Array: A Proposed Explorer Mission for Radio Astronomy (1999)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: A radio interferometer array in space providing high dynamic range images with unprecedented angular resolution over the broad frequency range from 0.030 - 30 MHz will open new vistas in solar, terrestial, galactic, and extragalactic astrophysics.
    Keywords: Astronomy
    Type: American Geophysical Union; United States
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    Cryocooler Options for Next Generation Space Telescope (NGST) and Other Space Applications (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We present a summary of cryocoolers that are presently available or in development and would be suitable for support of mid-infrared camera on the Next Generation Space Telescope.
    Keywords: Astronomy
    Type: Publications of the Astronomical Society of the Pacific
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    New VLA Observations for the HH 1-2 Region: Evidence for Density Enhancements Moving Along the Axis of the VLA 1 Radio Jet (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: Using the Very Large Array, we have carried out new, sensitive radio continuum observations at 6 and 3.6 cm of the HH 1-2 region. The comparison between the 6 cm maps made from data taken in 1986.2 and 1992.9 indicates that VLA 1, the exciting source of the HH 1-2 flow, has suffered a morphological change that is attributed to the motion of a symmetric pair of knots along the axis of the radio jet.
    Keywords: Astronomy
    Type: Astronomical Journal
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    Microarcsecond Astrometry as a Probe of Circumstellar Structure (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: 195th American Astronomical Society; Atlanta, GA; United States
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    Differential Astrometry of the 61 Cygni System with the Palomar Testbed Interferometer (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: American Astronomical Society; Atlanta, GA; United States
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    Differential Astrometry with the Keck Interferometer (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: Among the Keck Interferometer's high priority science programs will be the differential astrometric detection of planetary companions to nearby stars.
    Keywords: Astronomy
    Type: Working on the Fringe Conference; Dana Point, CA; United States
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    Predicting Stellar Angular Sizes (1999)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: Reliable prediction of stellar diameters, particularly angular diameters, is a useful and necessary tool for the increasing number of milliarcsecond resolution studies being carried out in the astronomical community.
    Keywords: Astronomy
    Type: Working on the Fringe Conference; Dana Point, CA; United States
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    Ferrate (VI) as a Possible Oxidant on the Martian Surface (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Proceedings of Bio-Astronomy|Bio-Astronomy; United States
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    New Millennium Program: Space Flight Validation of Advanced Technologies for Future Science Missions (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: 31st Annual Meeting of the Division of Planetary Sciences of the American Astronomical Society; Padua; Italy
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    A Three Dimensional Thermal Model of an Irregular Cometary Nucleus (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Division for Planetary Sciences Meeting of the American Astronomical Society; Padua; Italy
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    The Temporal Activity of IO's Hot Spots: Recent Results From Galileo (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Division for Planetary Sciences Meeting of the American Astronomical Society; Padova; Italy
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  • 68
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    Anticorrelation of 5-mue Brightness and Low Albedo Features in Jovian NEB (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Division for Planetary Sciences Meeting of the American Astronomical Society; Padua; Italy
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  • 69
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    Loki as Observed by the Near-Infrared Mapping Spectrometer (NIMS) (1999)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: The Galileo spacecraft has been observing Io throughout the Prime and Europa missions.
    Keywords: Astronomy
    Type: Division for Planetary Sciences Meeting of the American Astronomical Society; Padua; Italy
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  • 70
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    Probing Europa's Hidden Ocean From Tidal Effects on Orbital Dynamics (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: Indirect observations of Eurpoa suggest that the Jovian satellite may have a liquid ocean underneath its ice surface.
    Keywords: Astronomy
    Type: Division for Planetary Sciences Meeting of the American Astronomical Society; Padua; Italy
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  • 71
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    Practical Aspects of Calibration Near-Infrared Interferometer Data: Predicting Stellar Angular Sizes (1999)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: Reliable prediction of stellar diameters, particularly angular diameters, is a useful and necessary tool for the increasing number of milliarcsecond resolution studies being carried out in the astronomical community.
    Keywords: Astronomy
    Type: Publications of the Astronomical Society of the Pacific
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    Submillimeter Imaging of the Luminous Infrared Galaxy Pair VV114 (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We report on 450 and 850 mue observations of the interacting galaxy pair, VV114E+W (IC 1623), taken with the SCUBA camera on the James Clerk Maxwell Telescope, and near-infrared observations taken with UFTI on the UK Infrared Telescope.
    Keywords: Astronomy
    Type: Astronomical Journal
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    Cepheids in the Fornax Cluster Galaxy NGC 1365 (1997)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
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    8-13 Micron Spectroscopy of Young Stars (1997)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We present 8-13 mue spectra of 23 young Stars acquired with the UKIRT CGS3 spectrometer, including T Tauri, Herbig Ae/Be, and FU Ori Stars.
    Keywords: Astronomy
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    8-13 Micron Spectroscopy of Young Stars (1997)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We presen 8-13 meu spectra of 23 young stars acquired with the UKIRT CGS3 spectromere, including T Tauri, Herbig Ae/Be, and FU Ori stars. Silicate emission and absorption features can generally be matched with the Trapezium emissivity, by employing simple models to account for optical depth effects.
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    Close Approaches of Stars to the Solar System (1997)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
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    Probing the Photodissociation Region Toward HD200775 (1997)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: The illuminating source of the photodissociation region associated with the reflection nebula NGC7023 is HD200775. We probed the foreground atomic and molecular material through diagnostics observed in absorption against the background star.
    Keywords: Astronomy
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    Close Approaches of Stars to the Solar System (1997)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
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    The Colors of Young Asteriods (1997)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: Recent spectral observations of asteriods have identified a plausible origin for the ordinary chondrite meteorites (OCs). Owing to the paucity of main-belt asteriods with matching spectra [1], it had previously been difficult to explain their origin.
    Keywords: Astronomy
    Type: American Astronomical Society; Cambridge, MA; United States
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    Tip of the Red Giant Branch as a Distance Indicator (1997)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
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    Reconfigurable Pointing Control for High Resolution Space Spectroscopy (1997)
    In:  Other Sources
    Details
    Publication Date: 2018-06-11
    Description: In this paper, a pointing control performance criteria is established to suppport high resolution space spectroscopy. Results indicate that these pointing control requirements are very stringent, and would typically be difficult to meet using standard 3-axis spacecraft control. To resolve this difficulty, it is shown that performance can be significantly improved using a reconfigurable control architecture that switches among a small bankof detuned Kalman filters. The effectiveness of the control reconfiguration approach is demonstrated by example on the Space Infra-Red Telescope Facility (SIRTF) pointing system, in support of the InfraRed Spectrograph (IRS) payload.
    Keywords: Astronomy
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    ROSAT Imaging of GRB920525 and GRB930118 (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: For this effort we requested ROSAT images of two small gamma-ray burst (GRB) error boxes. Our goal was to search for sources that might be associated with the quiescent site of a GRB. More than 1000 GRBs have been detected in the twenty five years since their discovery, yet their origin remains a mystery. No real-time or quiescent counterparts at any wavelength have been identified as sources of GRBs despite considerable follow-up efforts. Ground based campaigns to examine GRB error boxes shortly after the bursts have revealed no transient, or highly variable objects at optical and radio wavelengths in the time period of more than 7 hours after the burst. Due to the heavy demand on X-ray satellite time, and the difficulty of re-scheduling observations, rapid follow-up observations at high energies have not been obtained as quickly as the ground based-efforts. In fact, X-ray images of GRB error boxes are normally obtained months-years after burst detection. The current fastest X-ray response time is over two weeks. Deep imaging of GRB error boxes at X-ray wavelengths is an additional observational approach that can be used to constrain models of the origin of GRBs. We combined the results of our investigation of the GRB920525 error box with that of a prior ROSAT PSPC observation of GRB910814 and submitted them for publication. We conclude that based upon our efforts and those of others, deep X-ray observations obtained long after the GRB are not likely to yield further productive results until smaller GRB error boxes become available. It may be possible to obtain such small error boxes in the near future from XTE, HETE and an augmented IPN.
    Keywords: Astronomy
    Type: NASA/CR-97-112988 , NAS 1.26:112988
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    OSSE observations of the ultraluminous infrared galaxies ARP 220 and MRK 273 (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The results of oriented scintillation spectrometer experiment (OSSE) observations of the ultraluminous infrared galaxies Arp 220 and Mrk 273 are reported. The pointings of Arp 220 and Mrk 273 concentrated on their upper limits. The gamma ray luminosities from these sources were found to be between one and two orders of magnitude smaller than the infrared luminosities. Multiwavelength luminosity spectra are produced from the radio to the gamma ray regime, and are compared with the typical multiwavelength spectra of active galactic nuclei. The lack of measured gamma ray emission provides no evidence for the existence of buried active galactic nuclei in these ultraluminous infrared galaxies, but is consistent with an origin of the infrared luminosity from starburst activity.
    Keywords: Astronomy
    Type: ; 447-450
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    RXTE observations of AGN (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The Rossi X-ray Timing Explorer (RXTE) observed three active galaxies during its in-orbit verification phase: NGC 4151; NGC 4945, and MCG 8-11-11. All three were detected from 2 keV to more than 100 keV by a combination of the proportional counter array (PCA) and the high energy X-ray timing experiment (HEXTE). The PCA contains five, xenon/methane, multilayer, multiwire, gas proportional counters covering the 2 to 60 keV range, while HEXTE is an array of eight NaI/CsI phoswich scintillation counters covering the 15 to 250 keV range. The three active galaxies represent the classes of Seyfert 1, Seyfert 2 and intermediate Seyfert galaxies. The results of the fitting of various models containing partial covering fractions, Compton reflection components and high energy spectral breaks are discussed.
    Keywords: Astronomy
    Type: ; 393-395
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    New COMPTEL results on pulsar studies at MeV energies (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The Compton telescope (COMPTEL) onboard the Compton Gamma Ray Observatory (CGRO) detected the pulsar PSR B1951-32 at MeV energies, and found indications of a signal from PSR B0656+14. In the combined spectra from COMPTEL and the energetic gamma ray experiment telescope (EGRET) onboard CGRO, it can be seen that the maximum luminosities of these objects are reached in the COMPTEL energy range. These spectra can be compared with those from four other pulsars observed in MeV energies with COMPTEL. The spectral properties of five of the six pulsars, Vela, PSR B1509-58, PSR B1951-32 and PSR B0656+14, require breaks and bends at MeV energies. The sixth pulsar, the Crab pulsar, approximately follows a power law flux relation from keV to GeV energies. It is concluded that this spectral behavior may play a role in the discrimination between current gamma ray emission models.
    Keywords: Astronomy
    Type: Proceedings of 2nd INTEGRAL Workshop 'The Transparent Universe'; 287-290; ESA-SP-382
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    Measuring the 511 keV emission in the direction of 1E1740.7-2942 with BATSE (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Observations of the 511 keV emission in the direction of 1E 1740.7-2942 (1E) using the earth burst and transient source experiment (BATSE) onboard the Compton Gamma Ray Observatory (CGRO), are presented. The CGRO phase 1 average spectrum of 1E is calculated using a method which assumes that a given source spectrum is the sum of the flux coming directly from the object and the contribution from the surrounding diffuse emission. The 1E light curve is calculated in the 40 to 150 keV range. It presents a constant flux excess of 70 mCrab in comparison with observations from the SIGMA gamma ray telescope onboard the GRANAT observatory. By removing this contribution, the 1E spectral transition from the low state to the high standard state observed by SIGMA is confirmed, and it is shown that the 511 keV flux is independent of the 1E long term evolution from low state to high standard state. It is concluded that the 511 keV emission of (4.2 +/- 1.3) x 140(exp -4) photons/sq cm s observed in the direction of 1E is mainly diffuse and spatially extended.
    Keywords: Astronomy
    Type: Proceedings of 2nd INTEGRAL Workshop 'The Transparent Universe'; 109-111; ESA-SP-382
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    Reduction of EUVE Guest Observer Data (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: We report on the observation of the HI filament LVC 88+36-2 with the Deep Survey/Spectrometers of EUVE. Detecting the shadow of this cloud in absorption might have proven the existence of a diffuse EUV background behind the cloud, and constrain the emission geometries of the hot plasma in the Local Interstellar Medium (LISM). By detecting diffuse emission in the EUVE spectrometers, it would also be possible to constrain the temperature and pressure of the emitting regions as well as determine whether or not the hot phase of the LISM is in equilibrium with cosmic elemental abundances. Unfortunately, we did not detect a cloud shadow with this set of observations. This is due to a combination of circumstances, but mostly due to the fact that EUV diffuse emission is weak compared to the background levels of EUVE. If a shadow exists in the EUVE, then it is less than 1% of the EUVE detector background of 1e-3 cts arcmin(exp -2) in the Deep Survey detector.
    Keywords: Astronomy
    Type: NASA-CR-205069 , NAS 1.26:205069
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    Deep WFPC2 and Ground-Based Imaging of a Complete Sample of 3C Quasars and Galaxies (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: We present the results of an HST and ground-based imaging study of a complete 3C sample of zeta approx. equal to 1 sources, comprising 5 quasars and 5 radio galaxies. We have observed all of the sample in essentially line-free bands at rest-frame 0.33 micrometers with WFPC2 and in rest-frame 1 micrometer images from the ground; we have also observed most of the sample in narrow-band filters centered on [O II]. We resolve continuum structure around all of our quasars in the high-resolution WFPC2 images, and in four of the five ground-based K' images. All of the quasars have some optical continuum structure that is aligned with the radio axis. In at least 3 of these cases, some of this optical structure is directly coincident with a portion of the radio structure, including optical counterparts to radio jets in 3C212 and 3C245 and an optical counterpart to a radio lobe in 3C2. These are most likely due to optical synchrotron radiation, and the radio and optical spectral indices in the northern lobe of 3C2 are consistent with this interpretation. The fact that we see a beamed optical synchotron component in the quasars but not in the radio galaxies complicates both the magnitude and the alignment comparisons. Nonetheless, the total optical and K' flux densities of the quasar hosts are consistent with those of the radio galaxies within the observed dispersion in our sample. The distributions of K' flux densities of both radio galaxies and quasar hosts exhibit similar mean and dispersion to that found for other radio galaxies at this redshift, and the average host galaxy luminosity is equivalent to, or a little fainter than, L*. The formal determination of the alignment in the optical and infrared in the two subsamples yields no significant difference between the radio galaxy and quasar subsamples, and the quasars 3C 196 and 3C 336 have aligned continuum and emission-line structure that is probably not due to beamed optical synchrotron emission. Very blue and/or edge-brightened structures are present in some objects within the probable quasar opening angle; these are possibly the result of illumination effects from the active nucleus, i.e., scattered quasar light or photoionization. In 3C 212, we see an optical object that lies 3 min. beyond the radio lobe, but which looks morphologically quite similar to the radio lobe itself. This object is bright in the infrared and has a steep spectral gradient along its length. A striking, semi-circular arc seen associated with 3C 280 may possibly be a tidal tail from a companion, enhanced in brightness by scattering or photoionization. In the near-infrared, most of the radio galaxies have elliptical morphologies with profiles that are well-fit by de Vaucouleurs r(exp 1/4)-laws and colors that are consistent with an old stellar population. All components around the quasars have optical-infrared colors that are redder than or similar to the colors of their respective nuclei; this is more consistent with a stellar origin for the emission than with a dominant scattering contribution. From the correspondence between the total magnitudes in the galaxies and quasars and the detection of aligned components in the quasars, we conclude that this study provides general support for the unification of FR II radio galaxies and quasars. Some of the objects in the sample (e.g, 3C 212) have properties that may be difficult to explain with our current understanding of the nature of FR II radio sources and the alignment effect.
    Keywords: Astronomy
    Type: NASA-CR-204783 , NAS 1.26:204783
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    Multi-Wavelength Monitoring of GRS 1915+105 (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Since its discovery in 1992, the superluminal X-ray transient GRS 1915+105 has been extensively observed in an attempt to understand its behaviour. We present here preliminary results from a multi-wavelength campaign undertaken from July to September 1996. This study includes X-ray data from the RXTE All Sky Monitor and BATSE, two-frequency data from the Nancay radio telescope, and infrared photometry from the 1.8m Perkins telescope at Lowell Observatory. The K-band data presented herein provide the first long-term well-sampled IR light curve of GRS 1915+105. We compare the various light curves, searching for correlations in the behaviour of the source at differing wavelengths and for possible periodicities.
    Keywords: Astronomy
    Type: NASA-TM-111176 , NAS 1.15:111176 , OUAST/97/9 , Compton; United States
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    Timing the Geminga Pulsar with High-Energy Gamma-Rays (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This is a continuing program to extend and refine the ephemeris of the Geminga pulsar with annual observations for the remaining lifetime of EGRET. The data show that every revolution of Geminga is accounted for during the EGRET epoch, and that a coherent timing solution linking the phase between EGRET, COS-B, amd SAS-2, observations has now been achieved. The accuracy of the gamma-ray timing is such that the proper motion of the pulsar can now be detected, consistent with the optical determination. The measured braking index over the 24.2 yr baseline is 17 +/- 1. Further observation is required to ascertain whether this very large braking index truly represents the energy loss mechanism, perhaps related to the theory in which Geminga is near its gamma-ray death line, or whether it is a manifestation of timing noise. Statistically significant timing residuals are detected in the EGRET data; they depart from the cubic ephemeris at a level of 23 milliperiods. The residuals appear to have a sinusoidal modulation with a period of about 5.1 yr. This could simply be a manifestation of timing noise, or it could be consistent with a planet of mass 1.7/sin i solar mass orbiting Geminga at a radius of 3.3/sin i AU.
    Keywords: Astronomy
    Type: NASA-CR-204445 , CAL-2639 , NAS 1.26:204445
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    Wavefront Analysis of Adaptive Telescope (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The motivation for this work came from a NASA Headquarters interest in investigating design concepts for a large space telescope employing active optics technology. The development of telescope optical requirements and potential optical design configurations is reported.
    Keywords: Astronomy
    Type: NASA-CR-204538 , NAS 1.26:204538
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    COMPTEL observations of GRO J1655-40 (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The transient black hole candidate GRO J1655-40 was shown elsewhere to eject matter at apparently superluminal velocities. The oriented scintillation spectrometer experiment (OSSE) spectra, measured during the X-ray outbursts, are consistent with a single power law up to 600 keV, with no evidence of a high energy cutoff. The detection of the flaring behavior of this source up to 10 MeV was claimed elsewhere. The Compton telescope (COMPTEL) observations in the 0.75 to 30 MeV band of this source are analyzed. The upper limits on the time averaged emission are presented and gamma ray flares are searched for. It is concluded that the COMPTEL data can neither confirm nor refute the claimed detection of a large gamma ray flare from this source. The gamma ray flare search in five years' worth of data did not reveal evidence for the occurrence of strong flares on timescales of two days.
    Keywords: Astronomy
    Type: Proceedings of 2nd INTEGRAL Workshop 'The Transparent Universe'; 225-228; ESA-SP-382
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  • 93
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    Infrared, submillimeter, and millimeter observations of the soft gamma-ray repeaters (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Soft gamma ray repeaters appear to be a new class of neutron stars. While a counterpart to SGR 0525-66 was detected uniquely in the X-ray band, SGR 1806-20 and SGR 1900+14 have unusual stellar counterparts whose spectra peak in the infrared. The infrared spectra appear to contain several components: the photospheric emission from stars dominates at shorter wavelengths; a bright point source dominates at 25 micrometers, and an extended source dominates at 60 micrometers. The longer wavelength spectra are inconsistent with mono-energetic synchrotron and black body radiation models. Recent millimeter, submillimeter and infrared observations are reviewed. A preliminary analysis of the higher resolution infrared spectra of SGR 1806-20 and SGR 1900+14 is outlined. These confirm previous observations suggesting that SGR1806-20 has an outflow and that the stars comprising the counterpart to SGR 1900+14 have very similar spectra.
    Keywords: Astronomy
    Type: ; 191-194
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  • 94
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    New COMPTEL results on the Orion/Monoceros region (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Results from recent observations of the Orion/Monoceros region, acquired with the Compton telescope (COMPTEL), are summarized, confirming previously reported results of excessive 3 to 7 MeV emission which is probably due to nuclear de-excitation lines from C-12 and O-16 nuclei following energetic nuclear interactions. The emphasis is on findings concerning the extent of the emission region. It is found that the emission extends over the entire cloud complex, although it may result from a few localized source regions. A preliminary spectrum is presented which indicates that the emission is widely spread over the 3 to 7 MeV range, suggesting a dominantly broadline origin from energetic C and O nuclei. The spectrum shows features that may be due to the splitting of the C and O lines.
    Keywords: Astronomy
    Type: Proceedings of 2nd INTEGRAL Workshop 'The Transparent Universe'; 71-74; ESA-SP-382
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  • 95
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    Total Solar Eclipse of 1999 August 11 (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: On 1999 August 11, a total eclipse of the Sun will be visible from within a narrow corridor which traverses the Eastern Hemisphere. The path of the Moon's umbral shadow begins in the Atlantic and crosses central Europe, the Middle East, and India, where it ends at sunset in the Bay of Bengal. A partial eclipse will be seen within the much broader path of the Moon's penumbral shadow, which includes northeastern North America, all of Europe, northern Africa, and the western half of Asia. Detailed predictions for this event are presented and include besselian elements, geographic coordinates of the path of totality, physical ephemeris of the umbra, topocentric limb profile corrections, local circumstances for approximately 1400 cities, maps of the eclipse path, weather prospects, the lunar limb profile, and the sky during totality. Tips and suggestions are also given on how to safely view and photograph the eclipse.
    Keywords: Astronomy
    Type: NASA-RP-1398 , NAS 1.61:1398 , Rept-97B00034
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  • 96
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    The Richness Dependence of Galaxy Cluster Correlations: Results From A Redshift Survey Of Rich APM Clusters (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: We analyze the spatial clustering properties of a new catalog of very rich galaxy clusters selected from the APM Galaxy Survey. These clusters are of comparable richness and space density to Abell Richness Class greater than or equal to 1 clusters, but selected using an objective algorithm from a catalog demonstrably free of artificial inhomogeneities. Evaluation of the two-point correlation function xi(sub cc)(r) for the full sample and for richer subsamples reveals that the correlation amplitude is consistent with that measured for lower richness APM clusters and X-ray selected clusters. We apply a maximum likelihood estimator to find the best fitting slope and amplitude of a power law fit to x(sub cc)(r), and to estimate the correlation length r(sub 0) (the value of r at which xi(sub cc)(r) is equal to unity). For clusters with a mean space density of 1.6 x 10(exp -6) h(exp 3) MpC(exp -3) (equivalent to the space density of Abell Richness greater than or equal to 2 clusters), we find r(sub 0) = 21.3(+11.1/-9.3) h(exp -1) Mpc (95% confidence limits). This is consistent with the weak richness dependence of xi(sub cc)(r) expected in Gaussian models of structure formation. In particular, the amplitude of xi(sub cc)(r) at all richnesses matches that of xi(sub cc)(r) for clusters selected in N-Body simulations of a low density Cold Dark Matter model.
    Keywords: Astronomy
    Type: OUAST/97/1 , Mont. Not. R. Astron. Soc.
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  • 97
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    Vela-like Pulsars: A Bridge Between Young and Old (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This grant was in support of a guest observation using the ASCA satellite of the young, spin-powered pulsar PSR B1706-44. The pulsar is interesting for several reasons: 1) it is young and shares many similar characteristics with the Vela pulsar, 2) it is one of a few pulsars which has been detected by the EGRET detector aboard the CGRO satellite, and 3) it is one of the confirmed sources of TeV gamma-rays discovered with ground based telescopes. The goals of the observation were to search for pulsations in the X-ray domain and to study the near stellar environment to determine if the pulsar is embedded within a compact nebula as in the case of the Vela pulsar.
    Keywords: Astronomy
    Type: NASA/CR-97-205790 , NAS 1.26:205790
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  • 98
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    The RS CVn Binary HD 155555: A Comparative Study of the Atmospheres for the Two Component Stars (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: We present GHRS/HST observations of the RS CVn binary system HD 155555. Several key UV emission lines (Fe XXI, Si IV, O V, C IV) have been analyzed to provide information about the heating rate throughout the atmosphere from the chromosphere to the corona. We show that both the G and K components reveal features of a chromosphere, transition region and corona. The emission measure distribution as a function of temperature for both components is derived and compared with the RS Cvn system, HR 1099, and the Sun. The transition region and coronal lines of both stars show nonthermal broadenings of approx. 20-30 km/s. Possible physical implications for coronal heating mechanisms are discussed.
    Keywords: Astronomy
    Type: NASA/CR-97-207188 , NAS 1.26:207188
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  • 99
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    Astronomical Software Directory Service (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: With the support of NASA's Astrophysics Data Program (NRA 92-OSSA-15), we have developed the Astronomical Software Directory Service (ASDS): a distributed, searchable, WWW-based database of software packages and their related documentation. ASDS provides integrated access to 56 astronomical software packages, with more than 16,000 URLs indexed for full-text searching. Users are performing about 400 searches per month. A new aspect of our service is the inclusion of telescope and instrumentation manuals, which prompted us to change the name to the Astronomical Software and Documentation Service. ASDS was originally conceived to serve two purposes: to provide a useful Internet service in an area of expertise of the investigators (astronomical software), and as a research project to investigate various architectures for searching through a set of documents distributed across the Internet. Two of the co-investigators were then installing and maintaining astronomical software as their primary job responsibility. We felt that a service which incorporated our experience in this area would be more useful than a straightforward listing of software packages. The original concept was for a service based on the client/server model, which would function as a directory/referral service rather than as an archive. For performing the searches, we began our investigation with a decision to evaluate the Isite software from the Center for Networked Information Discovery and Retrieval (CNIDR). This software was intended as a replacement for Wide-Area Information Service (WAIS), a client/server technology for performing full-text searches through a set of documents. Isite had some additional features that we considered attractive, and we enjoyed the cooperation of the Isite developers, who were happy to have ASDS as a demonstration project. We ended up staying with the software throughout the project, making modifications to take advantage of new features as they came along, as well as influencing the software development. The Web interface to the search engine is provided by a gateway program written in C++ by a consultant to the project (A. Warnock).
    Keywords: Astronomy
    Type: NASA/CR-97-207174 , NAS 1.26:207174
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  • 100
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    From Top to Bottom - the Multiwavelength Campaign of V824 Ara (HD 155555) (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A great deal of progress has been made in recent years in decomposing the 2-D structure in the atmospheres of late-type stars. Doppler images of many photospheres single stars, T Tauri stars, Algols, RS CV(sub n) binaries to name a few - are regularly published (Strassmeier 1996; Richards and Albright 1996; Rice and Strassmeier 1996; Kuerster et al. 1994). Ultraviolet spectral images of chromospheres appear in the literature (e.g., Walter et al. 1987; Neff et al. 1989) but are less common owing to the difficult nature of obtaining complete phase coverage. Zeeman doppler images of magnetic fields are now feasible (e.g., Donati et al. 1992). Performing Doppler imaging of the same targets over many seasons has also been accomplished (e.g, Vogt et al. 1997). Even when a true image reconstruction is not possible due to poor spectral resolution, we can still infer a great deal about spatial structure if enough phases are observed. However, it is increasingly apparent that to make sense of recent results, many different spectral features spanning a range of formation temperature and density must be observed simultaneously for a coherent picture to emerge. Here we report on one such campaign. In 1996, we observed the southern hemisphere RS CV(sub n) binary V824 Ara (P=1(sup d).68, G5IV+K0V-IV-IV) over one complete stellar rotation with the Hubble Space Telescope and EUVE. In conjunction, radio and optical photometry and spectroscopy were obtained from the ground. Unique to this campaign is the complete phase coverage of a number of activity proxy indicators that cover source temperatures ranging from the photosphere to the corona.
    Keywords: Astronomy
    Type: NASA/CR-97-207189 , NAS 1.26:207189
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