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  • 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)
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    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
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    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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    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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  • 6
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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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  • 7
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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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  • 8
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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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  • 9
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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
    Keywords: Astronomy
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  • 10
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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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  • 11
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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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  • 12
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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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  • 13
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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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  • 14
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    A Highly Doppler Blueshifted Fe-K Emission Line in the High-Redshift QSO PKS 2149-306 (1999)
    In:  CASI
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    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).
    Keywords: Astronomy
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  • 15
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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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  • 16
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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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  • 17
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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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  • 18
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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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  • 19
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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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  • 20
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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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  • 21
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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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  • 22
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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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  • 23
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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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  • 24
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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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    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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  • 26
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    Near/Mid Infrared-Wavelength Study of the Interacting Galaxy Pair UGC 12914/5 -- Taffy (1999)
    In:  Other Sources
    Details
    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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    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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  • 28
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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
    Details
    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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  • 35
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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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  • 36
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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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  • 38
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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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  • 39
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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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  • 41
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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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  • 42
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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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  • 43
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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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  • 44
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    Loki as Observed by the Near-Infrared Mapping Spectrometer (NIMS) (1999)
    In:  Other Sources
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    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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  • 45
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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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  • 46
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    Practical Aspects of Calibration Near-Infrared Interferometer Data: Predicting Stellar Angular Sizes (1999)
    In:  Other Sources
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    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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    Cassini Radio Science Experiments on Saturn and Titan Preserved Because of Lewis Analysis (1999)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: The Cassini mission to Saturn is an international venture with participation from NASA, the European Space Agency, and the Italian Space Agency. The Cassini spacecraft was launched from Cape Canaveral in October 1997 and is scheduled to arrive at Saturn in July 2004. After arrival, the spacecraft will orbit Saturn about 60 times over a period of 4 years. During this time, the Cassini Radio Science Subsystem will be used to investigate the atmosphere and rings of Saturn and the atmosphere of its largest moon, Titan--which is larger than Mercury and is the only moon in our solar system with a dense atmosphere. A critical component in Cassini s Radio Science Subsystem is a traveling-wave tube (TWT) that was designed at the NASA Lewis Research Center and built by Hughes Electronic Dynamics Division (ref. 1). This TWT will amplify downlink microwave signals at a frequency of 32 GHz for the Deep Space Network and will be involved in a number of experiments. These include occultation experiments in which the microwave signal will be beamed through rings and atmospheres toward Earth. Researchers will analyze the received signals to determine the sizes and distributions of the particles in the rings and the structure and composition of the atmospheres. The Radio Science Subsystem also will also be used to more accurately determine the mass and size of Saturn and its moons, to investigate the solar corona, and to search for gravity waves from outside the solar system.
    Keywords: Astronomy
    Type: Research and Technology 1998; NASA/TM-1999-208815
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    A Phase Shifting and Nulling Interferometer for TPF (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We present an interferometer design that provides a null at the star and a direct measurement of both visibility amplitude and phase of the planets.
    Keywords: Astronomy
    Type: Darwin and Astronomy, The Infrared Space Interferometer; Stockholm; Sweden
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    Amateur-Professional Cooperation: Lessons Learned From the International Halley Watch 1981-1989 (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: The International Halley Watch (IHW) was a focused coordination effort to obtain the most complete collection of data ever asembled on a comet.
    Keywords: Astronomy
    Type: Publications of the Astronomical Society of the Pacific
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    Modeling Viking Era Water Ice Clouds (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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    Europa's Thermal Emission (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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    Scientific Objectives and Capabilities of the DS2 Evolved Water Experiment (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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    Towards an Understanding of the Globular Cluster Over-abundance Around the Central Giant Elliptical NGC 1399 (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We investigate the kinematics of a combined sample of 74 globular clusters around NGC 1399.
    Keywords: Astronomy
    Type: The Astronomical Journal
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    Astrometry from Mutual Phenomena of the Galilean Satellites in 1990-1991 (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: The first extensive photometric observations of the mutual eclipses and occultations of the Galilean satellites date back to Jupiter's 1973 apparition.
    Keywords: Astronomy
    Type: Astronomical Journal
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    How can Wave Behavior Help Us Find Planets Around Distant Stars? (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: Here we will see how waves act in water. We will also see how the same kinds of wave behavior occur in other everday situations.
    Keywords: Astronomy
    Type: International Technolgoy Education Association; United States
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    Timing of Martian Magnetic Anomalies (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; Padua; Italy
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    The Deuterium Chemistry in a Protoplanetary Disk (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: International Astronomical Union (IAU) Symposium: 197: Astrochemistry from Molecular Clouds to Planetary Systems; Cheju; South Korea
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    Comet Simulation Experiments at JPL (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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    Contour: The Comet Nucleus Tour Mission (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: Target Selection: emphasis on diversity and unique objects. Flybys of three comets.
    Keywords: Astronomy
    Type: International Astronomical Union, Impact Workshop; Turin; Italy
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    An X-ray Selected Galaxy Cluster at z = 1.26 (sup 1,2) (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We report the discovery of an X-ray luminous galaxy cluster at z = 1.26.
    Keywords: Astronomy
    Type: The Astronomical Journal
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    Measuring the Granularity of the Diffuse X-ray Background (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: X-ray Astronomy 1999; United States
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    Spectral Gradients and u-v Sampling (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: I describe a systematic method for characterizing the effects of differences in u-v coverage in terms of inferred spectral gradients in interferometric images. This method is directly applicable to optical and radio interferometry; it is useful in situations when observations using scale arrays are not feasible.
    Keywords: Astronomy
    Type: Publications of the Astronomical Society of the Pacific
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    The Nature of the IRAS Ring G159.6-18.5 in Perseus and its Exciting Star HD 278942 (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We discuss an extended feature in the Perseus molecular cloud complex, most prominent in the IRAS database as an almost complete ring of radius 0.75 degrees, but also clearly seen in optical surveys and in radio continuum emission.
    Keywords: Astronomy
    Type: Astronomical Journal
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    Condensates in Jovian Atmospheres (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: Thermochemical equilibrium theory which starts with temperature/pressure profiles, compositional information and thermodynamic data for condensable species in the jovian planet atmospheres predicts layers of condensate clouds in the upper troposphere.
    Keywords: Astronomy
    Type: Publications of the Astronomical Society of the Pacific
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    Experimental Confirmation of Deep Nulling (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Darwin and Astronomy Conference; Stockholm; Sweden
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    Experimental Confirmation of Deep Nulling (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Darwin and Astronomy Conference; Stockholm; Sweden
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    The Search for Our Cosmic Roots and...Galactic Cousins (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: African Summit on Science and New Technologies; Pasadena, CA; United States
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    ISOCAM 15mum Search for Distant Infrared Galaxies Lensed by Clusters (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: In a search for lensed infrared galaxies, ISOCAM images have been obtained toward the rich clusters Abell 2218 and Abell 2219 at 15 micro m.
    Keywords: Astronomy
    Type: Astronomical Journal
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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 North/South Asymmetry in Interstellar Pick-up Hydrogen (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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    What Have we Already Learned From the CMB? (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: The Cosmic Background Explorer (COBE) satellite, and the Differential Microwave Radiometer (DMR) experiment in particular, was extraordinarily successful.
    Keywords: Astronomy
    Type: Publications of the Astronomical Society of the Pacific; United States
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    MIRO Capabilities and Calibration Approach (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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    Properties and Evolution of Disks Around Pre-Main-Sequence Stars of Intermediate Mass (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We discusses the properties of the immediate circumstellar environment of pre-main-sequence stars of intermediate mass, with particular emphasis of the properties and evolution of the circumstellar disks.
    Keywords: Astronomy
    Type: Protostars, Planets IV; United States
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    2MASS Extended Source Catalog: Overview and Algorithms (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: The 2 Micron All-Sky Survey (2MASS)will observe over one-million galaxies and extended Galactic sources covering the entire sky at wavelenghts between 1 and 2 m. Most of these galaxies, from 70 to 80%, will be newly catalogued objetcs.
    Keywords: Astronomy
    Type: Astronomical Journal
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    The AGN Content of the Two Micron All Sky Survey (1999)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: X-Ray Surveys and the History of Accretion in the Universe; Mentoporzio; Italy
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    The Determination and Long Term Integration of the Orbits of Caliban and Sycorax (1999)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: The first 2 irregular satellites of Uranus, Caliban and Sycorax, were discovered in late 1997. Subsequently, pre-discovery observations of both satellites were found on plates taken by D. Cruikshank in June of 1984. Recently, P. Nicholson, D. Tholen, and W. Offutt provided observations which they made in late 1998 at Palomar Mountain, Mauna Kea, and Cloudcroft, respectively. I fit a numerical integration perturbed by the Sun, Jupiter, Saturn, and Neptune to the set of available observations. For the 47 observations of Caliban the respective rms values of the Delta alpha (cos delta) and Delta delta residuals axe 0".60 and 0".32, and for the 103 observations of Sycorax the analogous values are 0".57 and 0".59. I extended the integration to span a 6000 year period and computed osculating orbital elements at yearly intervals. An included table contains the mean values of the elements over the 6000 years, the sidereal period, and the precession periods of the argument of periapsis and longitude of the ascending node. The osculating elements (except for a) exhibit a significant long period oscillation with a period roughly half that of the argument of periapsis.
    Keywords: Astronomy
    Type: Apr 28, 1999 - May 01, 1999; Estes Park, CO; United States
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    DK UMa: A Star on the Ascent (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: DK UMa (= 24 UMa = HD 82210) is a G4 IV-III star. According to its M(sub v) and B - V color, it is located at the base of the red giant branch, having recently exited from the Hertzsprung Gap. Now poised to start its first ascent along the giant branch, DK UMa is at a significant juncture in its post-main-sequence evolution, offering an important evolutionary comparison for magnetic activity with stars like 31 Comae, which is just entering the Hertzsprung Gap, and older stars like the Hyades giants or P Ceti, which have passed the tip of the giant branch and lie in the so-called 'clump'. As part of a major survey of the ultraviolet and X ray properties of a well-defined sample of evolved giant stars, DK UMa was observed with the Extreme Ultraviolet Explorer (EUVE) spacecraft in March 1997, for a total exposure time of 230 kiloseconds. A plot of the extracted short-wavelength (SW) spectrum of this star is shown, where it is compared with similar EUVE exposures for other yellow and red giant stars in the activity survey. In terms of the spectral lines of different ionization stages present in these spectra, the transition region and coronal temperature of DK UMa appears to be intermediate between those of 31 Com and P Ceti. Combining the relative strengths of the EUVE lines with Hubble Space Telescope (HST) data at near UV wavelengths and with ROSAT X-ray fluxes, the differential emission measure (DEM) distributions of these stars form a sequence in coronal temperature, which peaks at 10(exp 7.2) K for 31 Com, at 10(exp 6.8) K for B Ceti, and at intermediate temperatures for DK UMa - consistent with the evolutionary stages represented by the three stars. The integrated fluxes of the strongest emission lines found in the EUVE spectrum of DK UMa are listed, again compared with similar measurements for other giant stars that were observed in the course of other EUVE Guest Observer programs.
    Keywords: Astronomy
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  • 80
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    Adaptive Optics Imaging of Solar System Objects (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Most solar system objects have never been observed at wavelengths longer than the R band with an angular resolution better than 1". The Hubble Space Telescope itself has only recently been equipped to observe in the infrared. However, because of its small diameter, the angular resolution is lower than that one can now achieved from the ground with adaptive optics, and time allocated to planetary science is limited. We have successfully used adaptive optics on a 4-m class telescope to obtain 0.1" resolution images of solar system objects in the far red and near infrared (0.7-2.5 microns), at wavelengths which best discriminate their spectral signatures. Our efforts have been put into areas of research for which high angular reso!ution is essential.
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  • 81
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    Infrared Space Observatory Observations of Far-Infrared Rotational Emission Lines of Water Vapor Toward the Supergiant Star VY Canis Majoris (1999)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We report the detection of numerous far-infrared emission lines of water vapor toward the supergiant star VY Canis Majoris. A 29.5-45 micron grating scan of VY CMa, obtained using the Short-Wavelength Spectrometer (SWS) of the Infrared Space Observatory at a spectral resolving power lambda/delat.lambda of approximately 2000, reveals at least 41 spectral features due to water vapor that together radiate a total luminosity of approximately 25 solar luminosity . In addition to pure rotational transitions within the ground vibrational state, these features include rotational transitions within the (010) excited vibrational state. The spectrum also shows the (sup 2)product(sub 1/2) (J = 5/2) left arrow (sup 2)product(sub 3/2) (J = 3/2) OH feature near 34.6 micron in absorption. Additional SWS observations of VY CMa were carried out in the instrument's Fabry-Perot mode for three water transitions: the 7(sub 25)-6(sub 16) line at 29.8367 micron, the 4(sub 41)-3(sub 12) line at 31.7721 micron, and the 4(sub 32)-3(sub 03) line at 40.6909 micron. The higher spectral resolving power lambda/delta.lambda of approximately 30,000 thereby obtained permits the line profiles to be resolved spectrally for the first time and reveals the "P Cygni" profiles that are characteristic of emission from an outflowing envelope.
    Keywords: Astronomy
    Type: Astrophysical Journal; 517; L147-L150
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    SIRTF, the Space Infrared Telescope Facility (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Space Infrared Telescope Facility (SIRTF) is the last of the NASA Great Observatories, and a cornerstone of the NASA Origins Missions. The Observatory will include an 85 cm telescope in a unique orbit around the sun. The telescope will be launched at ambient temperature and cooled to 5.5K in space. The science instruments will use large detector arrays that will be background limited, and capable of a broad range of astrophysical investigations. The SIRTF architecture will accommodate up to 5 years of cryogenic space operations. This talk will describe both the scientific and technical capabilities of SIRTF.
    Keywords: Astronomy
    Type: 16th Instrumentation and Measurement Technology Conference; May 24, 1999; Venice; Italy
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  • 83
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    High Resolution X-Ray Explorer (HIREX) (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: SAO has carried out a study to determine the feasibility of building an orbiting telescope capable of resolving 7 km structure on the Sun. In order to achieve the required imaging the telescope must have a resolution 0.01 arcsec. This fact challenges the state of the art of orbiting telescopes in several areas: mirror figuring; optical metrology; optical mounting; mirror figure control; system alignment; optical stability; observatory pointing; and image stability image stability. The telescope design concept is based on a 0.6m Cassegrain-style telescope with a 240 meter effective focal length. This is achieved with 2 mirrors supported at opposite ends of a 27 m space-deployable boom. The telescope mirrors are coated with multilayers designed to reflect a broad XUV passband. A third, small mirror, near the focal plane performs the function of selecting the narrow band that is finally imaged. Image stabilization to the 0.005 a,rcsec level is achieved by active control of the secondary mirror. The primary mirror is held unadjustably to the spacecraft, its pointing set by the space- craft orientation. The secondary mirror is mounted on a 6-axis stage that permits its position to be changed to align the telescope in space. The stage is intended for intermittent adjustment, both because of its speed of travel, and the TBD alignment procedure. The third mirror is called the TXI (Tuneable X-ray Imager). It is mounted on a gimbal that permits it to be tipped over a 60 degree range, selecting between the individual wavelengths in the initial bandpass. It can also rotated completely out of the way to allow the full, broadband EUV flux to strike the focal plane.
    Keywords: Astronomy
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    New Mission Concepts for Astrophysics Large Area X-Ray Spectroscopy Mission (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Work at SAO was performed under the overall direction of Dr. Harvey Tananbaum, the Principal Investigator for the program. Dr. Jay Bookbinder was responsible for day to day program coordination at SAO and liaison with GSFC. Dr. Nicholas E. White served as GSFC Technical Officer for the Grant. The effort was directed at formulating the general characteristics and scientific requirements of the contemplated mission. While funding and therefore effort was limited, nonetheless SAO was involved in a broad range of activities. These activities were defined by our SAO proposal to GSFC that were subsequently accepted and funded by this Grant. The main activities were: Support of mission studies. Support the development of science requirements. and Performance of selected engineering studies and trades. During this period, an integrated GSFC/SAO management team began to form and work together. Jean F. Grady was appointed Project Formulation Manager at GSFC and assumed the overall management direction of the project including coordination of work performed under the grant.
    Keywords: Astronomy
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  • 85
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    Infrared Space Observatory (ISO) Key Project: the Birth and Death of Planets (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This program was designed to continue to analyze observations of stars thought to be forming protoplanets, using the European Space Agency's Infrared Space Observatory, ISO, as one of NASA Key Projects with ISO. A particular class of Infrared Astronomy Satellite (IRAS) discovered stars, known after the prototype, Vega, are principal targets for these observations aimed at examining the evidence for processes involved in forming, or failing to form, planetary systems around other stars. In addition, this program continued to provide partial support for related science in the WIRE, SOFIA and Space Infrared Telescope Facility (SIRTF) projects, plus approved ISO supplementary time observations under programs MCREE1 29 and VEGADMAP. Their goals include time dependent changes in SWS spectra of Long Period Variable stars and PHOT P32 mapping experiments of recognized protoplanetary disk candidate stars.
    Keywords: Astronomy
    Type: DU/Physics-5-34786
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  • 86
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    Hubble Space Telescope observations of Orion Nebula, Helix Nebula, and NGC 6822 (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This grant covered the major part of the work of the Principal Investigator and his collaborators as a Guaranteed Time Observer on the Hubble Space Telescope. The work done naturally divided itself into two portions the first being study of nebular objects and the second investigation of the interstellar medium between stars. The latter investigation was pursued through a contract with Princeton University, with Professor Lyman Spitzer as the supervising astronomer, assisted by Dr. Ed Fitzpatrick. Following the abrupt death of Professor Spitzer, his responsibilities were shifted to Dr. Fitzpatrick. When Dr. Fitzpatrick relocated to Villanova University the concluding work on that portion of this grant was concluded under a direct service arrangement. This program has been highly successful and the resulting publications in scientific journals are listed below. To the scientist, this is the bottom line, so that I shall simply try to describe the general nature of what was accomplished. There were three nebular programs conducted, one on the Orion Nebula, the second on the Helix Nebula, and the third on NGC 6822. The largest program was that on the Orion Nebula. This involved both HST observations and supporting groundbased observations obtained with a variety of instruments, including the Coude Feed Telescope at the Kitt Peak National observatory in Arizona, the Cerro Tololo observatory in Chile, and the Keck Observatory on Mauna Kea, Hawaii. Moreover, considerable theoretical modeling was done and all of the data analysis was performed at the Rice University in Houston, except for the PI's period of sabbatical leave (6-96 through 7-97) when he was based at the Max Planck Institute for Astronomy in Heidelberg, Germany. The Orion Nebula program was the most productive part, resulting in numerous papers, but more important in the discovery of a new class of objects, for which we coined the name "proplyds". The proplyds are protoplanetary disks surrounding very young stars still in the process of creation. The Orion Nebula is the residual material from a burst of star formation that occurred about 300,000 years ago. Each of these new stars has a surrounding disk of protoplanetary material. The same physics that renders the Nebula so highly visible means that the proto-planetary disks are also quite visible. With the wisdom of hindsight, we now see that this was to be expected and that we should have been searching specifically for this type of object. The discovery of these objects and their subsequent detailed investigation has lead to an accurate assessment of the frequency of protoplanetary disks in young stars and determination of the likelihood of survival of these disks into an era where planets actually form.
    Keywords: Astronomy
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    Discovery of a New Soft Gamma Repeater, SGR 1627-41 (1999)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: We report the discovery of a new soft gamma repeater (SGR), SGR 1627-41, and present BATSE observations of the burst emission and BeppoSAX Narrow-Field Instrument observations of the probable persistent X-ray counterpart to this SGR. All but one burst spectrum are well fit by an optically thin thermal bremsstrahlung model with kT values between 25 and 35 keV. The spectrum of the X-ray counterpart, SAX J1635.8-4736, is similar to that of other persistent SGR X-ray counterparts. We find weak evidence for a periodic signal at 6.41 s in the light curve for this source. Like other SGRs, this source appears to be associated with a young supernova remnant, G337.0-0.1. Based upon the peak luminosities of bursts observed from this SGR, we find a lower limit on the dipole magnetic field of the neutron star of B(sub dipole) approximately 〉 5 x 10(exp 14) G.
    Keywords: Astronomy
    Type: Astrophysical Journal; 519; L139-L142
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  • 88
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    A Multiwavelength Study of the Extreme AGN J2310-437 (1999)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: We present new X-ray, radio, and optical data for the unusual galaxy/cluster system J2310-437. Our results confirm the presence of an active nucleus and suggest an interpretation as an anomalous BL Lac object of bulk relativistic Doppler factor 〈2, with an optically deficient radio to X-ray spectrum. The radio, optical, and soft X-ray flux densities could lie along a single power-law function, lacking the curvature typical of BL Lac objects. Compared with other known sources that may have comparable multi-frequency spectra, J2310-437 is the most extreme. Its low isotropic optical/Ultraviolet (UV) radiation is consistent with the intensity of external photons governing the electron spectral break through Compton cooling; in this source the external photon density would be too low to produce a spectral break below the X-ray.
    Keywords: Astronomy
    Type: Astrophysical Journal; 516; 163-176
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  • 89
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    Galileo Net Flux Radiometer Data Analysis (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This report describes analysis of the Galileo Net Flux Radiometer (NFR), an instrument mounted on the Galileo probe, a spacecraft designed for entry into and direct measurements of Jupiter's atmosphere. The grant period for NAG2-1028 began on 1 April 1996, nearly four months after Jupiter atmospheric entry on 7 December 1995, and at which time the probe data were fully recovered and quick look analysis completed. This grant supported the detailed data analysis, resulting in a preliminary paper in Science in May 1996 and a final paper in the journal of Geophysical Research in .September 1998, with conference papers presented within this period.
    Keywords: Astronomy
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    Spectroscopic Observations of Steep Spectrum Narrow-Line Seyfert 1 Galaxies (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: ROSAT observations of narrow-line Seyfert 1s found consistently steep spectra and rapid variability, but ASCA observations show more diversity, very different to classical Seyfert 1s. However, in 3 NLS1s, ASCA finds common characteristics of these exciting new class of AGN (active galactic nuclei): a very strong high temperature soft excess, weak hard tail, a possible blue shifted ionized oxygen edge, and rapid large amplitude variability characterized by flares and quiescent periods. It is necessary to observe many more such objects in order to understand the physical processes underlying the different phenomenology in ASCA. ASCA observations of two NLS1s discovered by ROSAT's all sky survey were proposed and an observation of one of these objects, RX J0439-45, was awarded. The results of spectral and variability analysis are included in Leighly 1999ab, and preliminary results are found in Leighly 1998ab.
    Keywords: Astronomy
    Type: CAL-3120
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  • 91
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    X-Ray Observations of PKS 0558-504: A Test of Models for Narrow-Line Seyfert 1 Galaxies (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: ROSAT observations of narrow-line Seyfert 1 galaxies find a very steep soft spectrum and rapid variability. It has been suggested that these properties result from an extreme value of a yet unknown physical parameter; a high accretion rate, low black hole mass or face-on orientation have been suggested. During a Ginga observation of bright NLS1 PKS 0558-504, a flare was observed with rise time so rapid for this luminous object that the emission must be beamed. If reconfirmed, this behavior would support, the face-oil orientation model. PKS 0558-504 is one of the few NLS1s known to be bright enough above 10 keV that good spectral constraints on the reflection component, common in broad-line Seyfert 1s, is possible. A 60ks RXTE observation was performed; however, we failed to detect any large amplitude flares.
    Keywords: Astronomy
    Type: CAL-3122
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  • 92
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    Testing the Pair Reflection Model for AGN (1999)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: This project involved the interpretation of X-ray observations of AGN, and more specifically, evaluation and interpretation of the spectra in terms of the pair-reflection model. The grant was originally awarded on 3/14/94. We have now completed this work, which led to a number of publications. We found that reflection features are common in Seyfert galaxies, and may also be present in their radio-loud analogs, the broad-emission-line radio galaxies. In the latter case, however, a strong, nonthermal component is also present, and can swamp the thermal reflection spectrum.
    Keywords: Astronomy
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  • 93
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    A Reconnaissance of the 900-1200 A Spectra of Early O Stars in the Magellanic Clouds (1999)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Far-UV spectrograms of ten very hot stars in the Magellanic Clouds were obtained with the Hopkins Ultraviolet Telescope during the Astro-2 mission in March 1995. Very few normal OB stars were observed during Astro-1, and the only significant prior sample of such objects in this wavelength range was that obtained by Copernicus of stars near the Sun. The Magellanic Cloud sample offers the advantages of low reddening, a range in metallicity, and more extreme temperatures and luminosities than represented in the near solar neighborhood. Several interesting phenomena were found in the HUT MC sample, including very strong O VI wind profiles in O3 spectra; anomalous CNO wind features corresponding to abundances altered by stellar nucleosynthesis; weak wind features due to the metal deficiency of the Small Magellanic Cloud; and interstellar molecular hydrogen features originating in the MCs. The results were presented and discussed as a small atlas, and they were shown at the Pittsburgh AAS meeting in June 1995. A correlative atlas of Copernicus data was also prepared and published under the auspices of this grant. These publications will serve as resources for the characterization of the FUSE observations of related objects to hopefully be obtained soon. I believe that the large differences among the strong wind features in the HUT data, corresponding to CNO and systemic metallicity effects, are amenable to some relative quantitative analysis, and I shall endeavor to promote such in conjunction with HST data at longer wavelengths for the same stars (which has also not yet been completely analyzed) at a future opportunity.
    Keywords: Astronomy
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    A Polarimeter for SOFIA: Summary of Research (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The purpose of this research was to study designs for a far-infrared polarimeter for SOFIA that would greatly surpass the performance of the earlier polarimeter, Stokes, used on the Kuiper Airborne Observatory. Specifically we wished to gain the sensitivity to observe much fainter objects, to provide a choice of passbands, to reduce systematic errors, and to improve the efficiency. All of these objectives were successfully addressed. The gain in sensitivity will be achieved in part by the superior capabilities of SOFIA but to an even greater extent by the incorporation of new-technology detector arrays. We are developing superconducting transition-edge detectors using the "pop-up" design conceived by Dr. Harvey Moseley. The choice of passbands is achieved by providing three alternative optical paths, each with its own spectral filter, half-wave plate, and pupil tens. A new investigation has shown that multiwavelength observations provide an essential feature of far-infrared polarimetry. The principal source of systematic errors in observations of extended objects has been unknown polarization in the reference beams. We have developed a strategy for estimating these errors.
    Keywords: Astronomy
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  • 95
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    A Meeting on the AGN/Galaxy Connection (1999)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: This grant was used for travel support of several junior astronomers to attend the meeting "The Actice Galactic Nuclei (AGN)/Normal Galaxy Connection", Session El.2 of the 32nd COSPAR Assembly held in Nagoya, Japan, 12-19 July 1998. This meeting included the contributions from both theoretical and observational astronomers to the following fundamental questions: What causes the activity in galaxies? What is the difference between normal and active galaxies? Which processes are responsible for fueling the AGN? Do all galaxies have central Black Holes? What is the difference between low and high luminosity AGN? The observational papers discussed themes like: the detection of the black hole at the nucleus of our Galaxy, as well as in other galaxies; results from surveys of AGN in local galaxies, the source of their activity and their cold gas content; the observations of quasar host galaxies; the properties of Ultraluminous Infrared Galaxies. These papers used data from ground based observatories and several space missions (e.g. ASCA, ROSAT, HST, ISO) in wavebands from radio through gamma-rays. The theoretical papers discussed issues like: mechanisms to fuel the AGN; the physics of the accretion process; the formation of black-holes, quasars and their jets.
    Keywords: Astronomy
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    Mission Planning for the CHANDRA X-Ray Observatory (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The CHANDRA x-ray observatory started life as the Advanced X-ray Facility (AXAF) but was renamed Chandra in December of 1998 at the of a nationwide contest by NASA to name the new observatory. The honors the Nobel Prize winning astrophysicist S. Chandrasekar who astrophysics at the University of Chicago for more than 50 years, following graduate studies at Cambridge University in England. The observatory has been under construction for a decade under the management of the Observatory observatory, Projects office at the Marshall Space Flight Center; the same office that oversaw the construction of the Hubble Space Telescope and the Compton Gamma Ray Observatory. This observatory is a member of NASA's great observatory series of missions of which Hubble and Compton are members. This paper describes the mission planning that was conducted at MSFC to design the orbit and launch window that would permit the new observatory to function properly.
    Keywords: Astronomy
    Type: Astrodynamics Specialists Conference; Aug 16, 1999 - Aug 19, 1999; Girdwood, AK; United States
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  • 97
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    Investigating the Extraordinary X-Ray Variability of the Infrared Quasar IRAS 13349+2439 (1999)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: We observed the luminous quasar IRAS 13349+2439 using RXTE (X Ray Timing Explorer) in order to search for rapid variability. Unfortunately, the source was in a low state during the observation (PCA count rate approximately 1 - 2 counts/s). It was therefore somewhat weak for RXTE and detailed analysis proved to be difficult.
    Keywords: Astronomy
    Type: CAL-3119
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  • 98
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    Hard X-Ray and Wide Focusing Telescopes (1999)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The subject of this program are the development of two new type of X-ray telescopes, the wide field telescope, and the hard X-ray telescope.
    Keywords: Astronomy
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  • 99
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    Infrared Space Observatory (ISO) Data Analysis (1999)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Joseph is an ISO Co-Investigator. His Guaranteed Time Observations include both a major programme for which he is the Principal Investigator, and a number of other prgrammes in collaboration with other ISPHOT Co-Investigators, David Sanders, Alan Stockton, and Esther Hu.
    Keywords: Astronomy
    Type: Rept-6-52072 , Rept-6-53857 , Rept-6-53858 , Rept-6-54014 , Rept-6-54253
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  • 100
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    The Beta Pictoris Phenomenon in Young Stars With Accreting Gas (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Program Hae2BPIC resulted in usable ISO spectra of three young, Herbig Ae stars: HR 5999 (A7e, t=0.6 Myr), SV Cep (al-2e, t=1-3 Myr), and MW Vul (Al-2e, t=1-3 Myr). While too small a sample to pursue our original goal of surveying the silicate emission in these young, protoplanetary disk systems, comparison of these data with ground-based IR spectra, and published ISO observations of other HAe stars (especially the posters at PPIV) reveals the following: The known binary stars in the sample show signatures of partially crystal line silicate features by t=0.6 Myr, at an epoch when ostensibly single Herbig Ae stars have substantially stronger silicate emission dominated by amorphous grains. The known binary stars also show deficits in the optically thick continuum flux relative to coeval single stars. Comparison of ISO spectra indicates that the flux deficit seen in WD 163296 over 10-100 microns relative to AB Aur reflects a real deficit of material interior to 300.
    Keywords: Astronomy
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