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  • Astrophysics  (287)
  • Astronomy  (272)
  • Analytical Chemistry and Spectroscopy
  • Fisheries
  • Inorganic Chemistry
  • 2000-2004  (561)
  • 2002  (561)
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  • 2000-2004  (561)
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  • 1
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    Breakthrough of the year. The runners-up (2002)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2002-12-21
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉New York, N.Y. -- Science. 2002 Dec 20;298(5602):2297-303.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12493876" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Astronomical Phenomena ; Astronomy ; Biological Evolution ; Cosmic Radiation ; Elementary Particles ; Genome ; Hominidae ; Humans ; Ion Channels/physiology ; Lasers ; Light ; Microwaves ; Motion Pictures as Topic ; Optics and Photonics ; Retinal Ganglion Cells/physiology ; Rod Opsins/physiology ; *Science ; Sequence Analysis, DNA ; Temperature ; Tomography/methods
    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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    Support of marine sustainability science (2002)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2002-08-07
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ajayi, Thomas -- Sherman, Kenneth -- Tang, Qisheng -- New York, N.Y. -- Science. 2002 Aug 2;297(5582):772.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12162321" target="_blank"〉PubMed〈/a〉
    Keywords: Biomass ; Conservation of Natural Resources/*economics/*methods/trends ; *Ecosystem ; Europe ; Fisheries ; International Cooperation ; *Marine Biology/economics/trends ; North America ; Water Pollution/prevention & control
    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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    Breakthrough of the year. Scorecard 2002 (2002)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2002-12-21
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉New York, N.Y. -- Science. 2002 Dec 20;298(5602):2299.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12493878" target="_blank"〉PubMed〈/a〉
    Keywords: Astronomical Phenomena ; Astronomy ; Diagnostic Imaging ; Embryo, Mammalian/cytology ; Genetics, Medical ; Haplotypes ; Humans ; Optics and Photonics ; Proteomics ; *Science ; Stem Cells
    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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    Breakthrough of the year. Areas to watch in 2003 (2002)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2002-12-21
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉New York, N.Y. -- Science. 2002 Dec 20;298(5602):2298.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12493877" target="_blank"〉PubMed〈/a〉
    Keywords: Astronomical Phenomena ; Astronomy ; Biological Evolution ; Budgets ; Climate ; Elementary Particles ; Extraterrestrial Environment ; Ice ; Science/economics/*trends
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
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    A general model for designing networks of marine reserves (2002)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2002-12-10
    Description: There is debate concerning the most effective conservation of marine biodiversity, especially regarding the appropriate location, size, and connectivity of marine reserves. We describe a means of establishing marine reserve networks by using optimization algorithms and multiple levels of information on biodiversity, ecological processes (spawning, recruitment, and larval connectivity), and socioeconomic factors in the Gulf of California. A network covering 40% of rocky reef habitat can fulfill many conservation goals while reducing social conflict. This quantitative approach provides a powerful tool for decision-makers tasked with siting marine reserves.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sala, Enric -- Aburto-Oropeza, Octavio -- Paredes, Gustavo -- Parra, Ivan -- Barrera, Juan C -- Dayton, Paul K -- New York, N.Y. -- Science. 2002 Dec 6;298(5600):1991-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Center for Marine Biodiversity and Conservation, Scripps Institution of Oceanography, La Jolla, CA 92093, USA. esala@ucsd.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12471258" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; California ; Computer Simulation ; *Conservation of Natural Resources ; *Ecosystem ; Environment ; Fisheries ; Fishes ; Invertebrates ; *Models, Biological ; *Seawater
    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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  • 6
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    SNC Meteorites and Martian Reservoirs (2002)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Jones first suggested that the inverse covariation of initial epsilon (Nd-143) and Sr-87/Sr-86 of the shergottites could be explained by interaction between mantle-derived magmas with another isotopic reservoir(s) (i.e., assimilation or contamination). In that model, magmas were generated in a source region that was isotopically similar to the Nakhla source and the second reservoir(s) was presumed to be crust. The text also permitted the second reservoir to be another type of mantle, but I can confirm that a second mantle reservoir was never seriously considered by that author. Other features of this model were that (i) it occurred at a particular time, 180 m.y. ago, and (ii) the interacting reservoirs had been separated at approximately 4.5 b.y. In a later paper Jones explored this mixing model more quantitatively and concluded that magmas from a Nakhla-like source region at 180 m.y. would fall on or near an isotopic Nd-Sr-Pb hyperplane defined by the shergottites. This criterion was a necessary prerequisite for the parent magma(s) of the shergottites to have initially been Nakhla-like isotopically. At this juncture, it is perhaps worthwhile to note that this mixing model was not presented to explain geochemical variations but as a justification for a 180 m.y. crystallization age for the shergottites and a 1.3 b.y. crystallization age for the nakhlites. In the mid-1980's crystallization ages estimated for Nakhla ranged from approximately 1.3 b.y to 4.5 b.y. Similarly, preferred crystallization ages for the shergottites ranged from 360 m.y., to 1.3 b.y., to 4.5 b.y. In all these models, the 180 m.y. event seen in the shergottites was deemed to be metamorphic. The fit between the Nakhla-like source region and the shergottite hyperplane was a validation both of the 1.3 b.y. igneous age of Nakhla and the 180 m.y. igneous age of the shergottites.
    Keywords: Astrophysics
    Type: Unmixing the SNCs: Chemical, Isotopic, and Petrologic Components of the Martian Meteorites; 27-28; LPI-Contrib-1134
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  • 7
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    Groundbased Radar Investigations of Asteroids and Planetary Satellites (2002)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Radar is a powerful source of information about the physical and dynamical properties of solar system bodies. Radar-detected targets include the Moon, Mercury, Mars, Venus, Phobos, Io, Europa, Ganymede, Callisto, Titan, Iapetus, Saturn's rings, eight comets, and 179 asteroids (75 main-belt and 104 near-Earth). This talk offers a perspective on the disc-integrated radar properties of solar system bodies and then turns to what radar remote sensing can tell us about asteroids using spatially-resolved measurements.
    Keywords: Astrophysics
    Type: Solar System Remote Sensing; 59-60; LPI-Contrib-1129
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  • 8
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    Labview Implementation of Image Processing and Phasing Control for the SIBOA Segmented Mirror Testbed (2002)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: 'NASA is preparing to launch the Next Generation Space Telescope (NGST). This telescope will be larger than the Hubble Space Telescope, be launched on an Atlas missile rather than the Space Shuttle, have a segmented primary mirror, and be placed in a higher orbit. All these differences pose significant challenges.' This effort addresses the challenge of implementing an algorithm for aligning the segments of the primary mirror during the initial deployment that was designed by Philip Olivier and members of SOMTC (Space Optics Manufacturing Technology Center). The implementation was to be performed on the SIBOA (Systematic Image Based Optical Alignment) test bed. Unfortunately, hardware/software aspect concerning SIBOA and an extended time period for algorithm development prevented testing before the end of the study period. Properties of the digital camera were studied and understood, resulting in the current ability of selecting optimal settings regarding saturation. The study was successful in manually capturing several images of two stacked segments with various relative phases. These images can be used to calibrate the algorithm for future implementation. Currently the system is ready for testing.
    Keywords: Astronomy
    Type: Research Reports: 2001 NASA/ASEE Summer Faculty Fellowship Program; XLII-1 - XLII-5; NASA/CR-2002-211840
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  • 9
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    Science Outreach at NASA's Marshall Space Flight Center (2002)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: At the end of World War II Duane Deming, an internationally known economist enunciated what later came to be called "Total Quality Management" (TQM). The basic thrust of this economic theory called for companies and governments to identify their customers and to do whatever was necessary to meet their demands and to keep them satisfied. It also called for companies to compete internally. That is, they were to build products that competed with their own so that they were always improving. Unfortunately most U.S. corporations failed to heed this advice. Consequently, the Japanese who actively sought Deming's advice and instituted it in their corporate planning, built an economy that outstripped that of the U.S. for the next three to four decades. Only after U.S. corporations reorganized and fashioned joint ventures which incorporated the tenets of TQM with their Japanese competitors did they start to catch up. Other institutions such as the U.S. government and its agencies and schools face the same problem. While the power of the U.S. government is in no danger of being usurped, its agencies and schools face real problems which can be traced back to not heeding Deming's advice. For example, the public schools are facing real pressure from private schools and home school families because they are not meeting the needs of the general public, Likewise, NASA and other government agencies find themselves shortchanged in funding because they have failed to convince the general public that their missions are important. In an attempt to convince the general public that its science mission is both interesting and important, in 1998 the Science Directorate at NASA's Marshall Space Flight Center (MSFC) instituted a new outreach effort using the interact to reach the general public as well as the students. They have called it 'Science@NASA'.
    Keywords: Astronomy
    Type: Research Reports: 2001 NASA/ASEE Summer Faculty Fellowship Program; XXIX-1 - XXIX-5; NASA/CR-2002-211840
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  • 10
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    Photometric Modeling of a Cometary Nucleus: Taking Hapke Modeling to the Limit (2002)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: In the past two decades, photometric models developed by Bruce Hapke have been fit to a wide range of bodies in the Solar System: The Moon, Mercury, several asteroids, and many icy and rocky satellites. These models have enabled comparative descriptions of the physical attributes of planetary surfaces, including macroscopic roughness, particle size and size-distribution, the single scattering albedo, and the compaction state of the optically active portion of the regolith. One challenging type of body to observe and model, a cometary nucleus, awaited the first space based mission to obtain images unobscured by coma. The NASA-JPL Deep Space 1 Mission (DS1) encountered the short-period Jupiter-family comet 19/P Borrelly on September 22, 2001, about 8 days after perihelion. Prior to its closest approach of 2171 km, the remote-sensing package on the spacecraft obtained 25 CCD images of the comet, representing the first closeup, unobscured view of a comet's nucleus. At closest approach, corresponding to a resolution of 47 meters per pixel, the intensity of the coma was less than 1% of that of the nucleus. An unprecedented range of high solar phase angles (52-89 degrees), viewing geometries that are in general attainable only when a comet is active, enabled the first quantitative and disk-resolved modeling of surface photometric physical parameters.
    Keywords: Astrophysics
    Type: Solar System Remote Sensing; 7; LPI-Contrib-1129
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  • 11
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    Experimental Validation of a Neuro-Fuzzy Approach to Phasing the SIBOA Segmented Mirror Testbed (2002)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: NASA is preparing to launch the Next Generation Space Telescope (NGST). This telescope will be larger than the Hubble Space Telescope, be launched on an Atlas missile rather than the Space Shuttle, have a segmented primary mirror, and be placed in a higher orbit. All these differences pose significant challenges. This effort addresses the challenge of aligning the segments of the primary mirror during the initial deployment. The segments need to piston values aligned to within one tenth of a wavelength. The present study considers using a neuro-fuzzy model of the Fraunhofer diffraction theory. The intention of the current study was to experimentally verify the algorithm derived earlier. The experimental study was to be performed on the SIBOA (Systematic Image Based Optical Alignment) test bed. Unfortunately the hardware/software for SIBOA was not ready by the end of the study period. We did succeed in capturing several images of two stacked segments with various relative phases. These images can be used to calibrate the algorithm for future implementation. This effort is a continuation of prior work. The basic effort involves developing a closed loop control algorithm to phase a segmented mirror test bed (SIBOA). The control algorithm is based on a neuro-fuzzy model of SIBOA and incorporates nonlinear observers built from observer banks. This effort involves implementing the algorithm on the SIBOA test bed.
    Keywords: Astronomy
    Type: Research Reports: 2001 NASA/ASEE Summer Faculty Fellowship Program; XXXVIII-1 - XXXVIII-5; NASA/CR-2002-211840
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  • 12
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    Image Dis-Integration for Improved Plasmasphere Visualization (2002)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Traditionally, study of the plasmasphere has involved terrestrial observation of local characteristics. Global modeling of the plasmasphere in such an observation regime made use of an ensemble of (sparse) local measurements. Recently, sensors aboard the IMAGE (Imager for Magnetopause-to-Aurora Global Exploration) satellite (in particular, the EUV (Extreme Ultra Violet) Imager) have created the potential for truly global study of the plasmasphere. IMAGE was launched in spring of 2000 in an orbit with apogee altitude 7.2 RE(Earth radii) and perigee altitude 1000 km. IMAGE's EUV sensor allows an external view of the distribution of cold plasma in the plasmasphere to be acquired. EUV is designed to image light emission at 30.4 nanometers, which is the emission wavelength of the He+ ion in the presence of solar radiation. He+ makes up approximately 15-20% of the plasma in the plasmasphere, thus imaging of He+ enables determination of plasma distribution. The EUV instrument provides a 90 deg by 84 deg field of view which is imaged as an equally spaced 150x140 pixel array on a spherical imaging surface. The EUV produces an image approximately every 10 minutes when the sensor is operating. Since EUV images contain line-of-sight integrations of plasma distributions, they do not directly express equatorial plane density (which would enable comparison of observed plasma distributions with predictions from models). Furthermore, the plasma density at any point in three-space is not known. The goal of our work was development of a technique that can enable plasma density to be determined throughout three-space. Our approach to creation of a three-space representation of the plasma distribution involves disintegrating the EUV lines of sight to form a volumetric map of plasma densities.
    Keywords: Astronomy
    Type: Research Reports: 2001 NASA/ASEE Summer Faculty Fellowship Program; XXXVI-1 - XXXVI-5; NASA/CR-2002-211840
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  • 13
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    Far Ultraviolet Astronomy (2002)
    In:  CASI
    Details
    Publication Date: 2009-05-17
    Description: The Far Ultraviolet Spectroscopic Explorer (FUSE) is studying a wide range of astronomical problems in the 905-1187 Angstrom wavelength region through the use of high resolution spectroscopy. The FUSE bandpass forms a nearly optimal complement to the spectral coverage provided by the Hubble Space Telescope (HST), which extends down to approximately 1170 Angstroms. The photoionization threshold of atomic hydrogen (911 Angstroms) sets a natural short-wavelength limit for the FUV. FUSE was launched in June 1999 from Cape Canaveral, Florida, on a Delta II rocket into a 768 km circular orbit. Scientific observations started later that year. This spectral region is extremely rich in spectral diagnostics of astrophysical gases over a wide range of temperatures (100 K to over 10 million K). Important strong spectral lines in this wavelength range include those of neutral hydrogen, deuterium, nitrogen, oxygen, and argon (H I, D I, N I, O I, and Ar I), molecular hydrogen (H2), five-times ionized oxygen (O VI), and several ionization states of sulfur (S III - S VI). These elements are essential for understanding the origin and evolution of the chemical elements, the formation of stars and our Solar System, and the structure of galaxies, including our Milky Way. FUSE is one of NASA's Explorer missions and a cooperative project of NASA and the space agencies of Canada and France. These missions are smaller, more scientifically focused missions than the larger observatories, like Hubble and Chandra. FUSE was designed, built and operated for NASA by the Department of Physics and Astronomy at Johns Hopkins University. Hundreds of astronomers world-wide are using FUSE for a wide range of scientific research. Some of the important scientific discoveries from the first two years of the mission are described.
    Keywords: Astronomy
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  • 14
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    Asteroseismology from Space: The Delta Scuti Star Theta(sup 2) Tauri Monitored by the WIRE Satellite (2002)
    In:  CASI
    Details
    Publication Date: 2004-10-05
    Description: The bright variable star theta(sup 2) Tau was monitored with the star camera on the Wide-Field Infrared Explorer satellite. Twelve independent frequencies were detected down to the 0.5 mmag amplitude level. Their reality was investigated by searching for them using two different algorithms and by some internal checks: both procedures strengthened our confidence in the results. All the frequencies are in the range 10.8-14.6 cd(exp -1). The histogram of the frequency spacings shows that 81% are below 1.8 d; rotation may thus play a role in the mode excitation. The fundamental radial mode is not observed, although it is expected to occur in a region where the noise level is very low (55 mu mag). The rms residual is about two times lower than that usually obtained from successful groundbased multisite campaigns. The comparison of the results of previous campaigns with the new ones establishes the amplitude variability of some modes.
    Keywords: Astronomy
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  • 15
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    X-ray Dips Followed by Superluminal Ejections as Evidence for An Accretion Disc Feeding the Jet in A Radio Galaxy (2002)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Accretion onto black holes is thought to power the relativistic jets and other high-energy phenomena in both active galactic nuclei (AGNs) and the "microquasar" binary systems located in our Galaxy. However, until now there has been insufficient multifrequency monitoring to establish a direct observational link between the black hole and the jet in an AGE. This contrasts with the case of microquasars, in which superluminal features appear and propagate down the radio jet shortly after sudden decreases in the X-ray flux. Such an X-ray dip is most likely caused by the disappearance of a section of the inner accretion disc, part of which falls past the event horizon and the remainder of which is injected into the jet. This infusion of energy generates a disturbance that propagates down the jet, creating the appearance of a superluminal bright spot. Here we report the results of three years of intensive monitoring of the X-ray and radio emission of the Seyfert-like radio galaxy 3C 120. As in the case of microquasars, dips in the X-ray emission are followed by ejections of bright superluminal knots in the radio jet. Comparison of the characteristic length and time scales allows us to infer that the rotational states of the black holes in these two objects are different.
    Keywords: Astrophysics
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  • 16
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    Differential Cratering of Synchronously Rotating Satellites by Ecliptic Comets (2002)
    In:  Other Sources
    Details
    Publication Date: 2011-08-23
    Description: We use Monte Carlo methods to simulate impacts of ecliptic comets on the synchronously rotating satellites of giant planets. We reconfirm the long-standing prediction that the cratering rate should be much higher on the leading hemispheres than on the trailing hemisphere; indeed we find that previously published analytical formulations modestly underestimate the degree of apex-antapex asymmetry to be expected. We then compare our results to new mapping of impact craters on Ganymede, Callisto, and Triton. Ganymede reveals a pronounced apex-antapex asymmetry that is nonetheless much less than predicted. All of Triton's confirmed impact craters are clustered toward the apex of motion, far exceeding the predicted asymmetry. No asymmetry is observed on Callisto. In each case at least one of our basic assumptions must be wrong. Likely candidates include the following: (i) the surfaces of all but the most sparsely cratered satellites are saturated or nearly saturated with impact craters; (ii) these satellites have rotated nonsynchronously over geological time; (iii) most of the craters are made not by heliocentric (Sun-orbiting) comets and asteroids but rather by planetocentric (planet-orbiting) debris of indeterminate origin; or (iv) pathological endogenic resurfacing has created illusions of structure. Callisto's surface is readily classified as nearly saturated. Ganymede's bright terrains, although less heavily cratered than those of Callisto, can also be explained by crater densities approaching saturation on a world where endogenic processes were active. The leading alternative is nonsynchronous rotation, an explanation supported by the distribution of catenae (crater chains produced by impact of tidally disrupted comets). Triton's craters can be explained by planetocentric debris or by capricious resurfacing, but both hypotheses are inherently improbable.
    Keywords: Astrophysics
    Type: Icarus (ISSN 0019-1035); Volume 153; 111-129
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  • 17
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    Serendipitous Detections of XTE J1906+09 with the Rossi X-Ray Timing Explorer (2002)
    In:  Other Sources
    Details
    Publication Date: 2011-08-23
    Description: The 89 s X-ray pulsar XTE J1906+09 was discovered during Rossi X-Ray Timing Explorer (RXTE) observations of SGR 1900+14 in 1996. Because of monitoring campaigns of SGR 1900+14, XTE J1906+09 was also monitored regularly in 1996 September, 1998 May-June, 1998 August-1999 July, and 2000 March-2001 January. A search for pulsations resulted in detections of only the two previously reported outbursts in 1996 September and 1998 August-September. Pulsed flux upper limits for the rest of the observations show that XTE J1906+09 is a transient X-ray pulsar and likely has a Be star companion. The RXTE all-sky monitor did not reveal XTE J1906+09. Pulse-timing analysis of the second outburst discovered a sinusoidal signature in the pulse frequencies that is likely produced by an orbital periastron passage. Fits to pulse phases using an orbital model and quadratic phase model have chi(exp 2) minima at orbital periods of 26-30 days for fixed mass functions of 5, 10, 15, and 20 solar masses. The pulse shape showed energy- and intensity-dependent variations. Pulse-phase spectroscopy quantified the energy-dependent variations. The phase-averaged spectrum used the pulse minimum spectrum as the background spectrum to eliminate effects from SGR 1900+14 and the Galactic ridge and was well fitted by an absorbed power law with a high-energy cutoff with column density N(sub H) = 6 +/- 1 x 10(exp 22)/sq cm, a photon index of 1.01 +/- 0.08, cutoff energy E(sub cut) = 11 +/- 1 keV, and e-folding energy E(sub fold) = 19 +/- 4 keV. Estimated 2-10 keV peak fluxes, corrected for contributions from the Galactic ridge and SGR 1900+14, are 6 x l0(exp -12) and 1.1 x 10(exp -10) ergs/sq cm/s for the 1996 and 1998 outbursts, respectively. XTE J1906+09 may be part of an unusual class of Be/X-ray binaries that do not lie on the general spin period versus orbital period correlation with the majority of Be/X-ray binaries.
    Keywords: Astronomy
    Type: The Astrophysical Journal; Volume 565; 1150-1160
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  • 18
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    Bulk X-ray Doppler Velocities in the Supernova Remnant Cassiopeia A (2002)
    In:  Other Sources
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    Publication Date: 2011-08-23
    Description: We map the average line-of-sight velocities of the X-ray-emitting mass in the supernova remnant Cassiopeia A using measurements of the centroid of the Si-Healpha blend with the Advanced CCD Imaging Spectrometer on the Chandra X-Ray Observatory. This 4 inch scale map confirms the broad trends noted in previous studies, namely, that the line-of-sight velocity scale is roughly 2000-3000 kilometers per second with relatively more blueshifted material in the southeastern region of the remnant than in the northwest; new details are that the northwestern region consists of two arcs, with the southernmost one representing the most redshifted X-ray-emitting material in Cas A. These results are consistent with contemporaneous results from XMM-Newton. The X-ray patterns resemble the complex velocity patterns measured at optical wavelengths for much denser ejecta, and they support the growing body of evidence that the explosion and subsequent evolution of Cas A were highly asymmetrical.
    Keywords: Astronomy
    Type: The American Astrophysical Society; Volume 560; L175-L179
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  • 19
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    Discovery of a 450 Hz Quasi-Periodic Oscillation from the Microquasar GRO J1655-40 with the Rossi X-ray Timing Explorer (2002)
    In:  Other Sources
    Details
    Publication Date: 2011-08-23
    Description: We report the discovery with the Proportional Counter Array on board the Rossi X-Ray Timing Explorer of a 450 Hz quasi-periodic oscillation (QPO) in the hard X-ray flux from the Galactic microquasar GRO J1655-40. This is the highest frequency QPO modulation seen to date from a black hole. The QPO is detected only in the hard X-ray band above approx. 13 keV. It is both strong and narrow, with a typical rms (root mean square) amplitude of 4.5% in the 13-27 keV range and a width of approx. 40 Hz (FWHM). For two observations in which we detect the 450 Hz QPO, a previously known approx. 300 Hz QPO is also observed in the 2-13 keV band. We show that these two QPOs sometimes appear simultaneously, thus demonstrating the first detection of a pair of high-frequency QPOs in a black hole system. Prior to this, pairs of high-frequency QPOs have been detected only in neutron star systems. GRO J1655-40 is one of only a handful of black hole systems with a good dynamical mass constraint. For a nonrotating black hole with mass between 5.5 and 7.9 solar masses, the innermost stable circular orbit (ISCO) ranges from 45 to 70 km. For any mass in this range the radius at which the orbital frequency reaches 450 Hz is less than the ISCO radius, indicating that, if the modulation is caused by Kepler motion, the black hole must have appreciable spin. If the QPO frequency is set by the orbital frequency of matter at the ISCO, then for this mass range the dimensionless angular momentum lies in the range 0.15 〈 j 〈 0.5. Moreover, if the modulation is caused by oscillation modes in the disk or Lense-Thirring precession, then this would also require a rapidly rotating hole. We briefly discuss the implications of our findings for models of X-ray variability in black holes and neutron stars.
    Keywords: Astrophysics
    Type: Astrophysical Journal; Volume 552; L49-L53
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    Pulsar Polar Cap Heating and Surface Thermal X-ray Emission (2002)
    In:  Other Sources
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    Publication Date: 2011-08-23
    Description: We investigate the effect of pulsar polar cap (PC) heating produced by positrons returning from the upper pair formation front. Our calculations are based on a self-consistent treatment of the pair dynamics and the effect of electric field screening by the returning positrons. We calculate the resultant X-ray luminosities and discuss the dependence of the PC heating efficiencies on pulsar parameters, such as characteristic spin-down age, spin period, and surface magnetic field strength. In this study we concentrate on the regime where the pairs are produced in a magnetic field by curvature photons emitted by accelerating electrons. Our theoretical results are not in conflict with the available observational x-ray data and suggest that the effect of PC heating should significantly contribute to the thermal x-ray fluxes from middle-aged and old pulsars. The implications for current and future x-ray observations of pulsars are briefly outlined.
    Keywords: Astronomy
    Type: The Astrophysical Journal; Volume 556; 987-1001
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    Computational Relativistic Astrophysics Using the Flow Field-Dependent Variation Theory (2002)
    In:  Other Sources
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    Publication Date: 2011-08-23
    Description: We present our method for solving general relativistic nonideal hydrodynamics. Relativistic effects become pronounced in such cases as jet formation from black hole magnetized accretion disks which may lead to the study of gamma-ray bursts. Nonideal flows are present where radiation, magnetic forces, viscosities, and turbulence play an important role. Our concern in this paper is to reexamine existing numerical simulation tools as to the accuracy and efficiency of computations and introduce a new approach known as the flow field-dependent variation (FDV) method. The main feature of the FDV method consists of accommodating discontinuities of shock waves and high gradients of flow variables such as occur in turbulence and unstable motions. In this paper, the physics involved in the solution of relativistic hydrodynamics and solution strategies of the FDV theory are elaborated. The general relativistic astrophysical flow and shock solver (GRAFSS) is introduced, and some simple example problems for computational relativistic astrophysics (CRA) are demonstrated.
    Keywords: Astrophysics
    Type: The Astrophysical Journal Supplement Series; Volume 139; 539-563
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  • 22
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    ASCA Observation of the Quiescent X-ray Counterpart to SGR 1627-41 (2002)
    In:  Other Sources
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    Publication Date: 2011-08-23
    Description: We present a 2-10 keV ASCA (Advanced Satellite for Cosmology and Astrophysics) observation of the field around the soft gamma repeater SGR 1627-41. A quiescent X-ray source, whose position is consistent both with that of a recently discovered BeppoSAX X-ray source and with the Interplanetary Network localization for this soft gamma repeater, was detected in this observation. In 2-10 keV X-rays, the spectrum of the X-ray source may be fit equally well by a power-law, blackbody, or bremsstrahlung function, with unabsorbed flux equal to approximately 5 x 10(exp -12) ergs cm(exp -2) s(exp -1). We do not confirm a continuation of a fading trend in the flux, and we find no evidence for periodicity, both of which were noted in the earlier BeppoSAX observations.
    Keywords: Astronomy
    Type: Astrophysical Journal; Volume 528; L21-L23
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  • 23
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    BATSE Observations of Gamma-Ray Burst Tails (2002)
    In:  Other Sources
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    Publication Date: 2011-08-23
    Description: With the observation of low-energy radiation coming from the site of gamma-ray bursts in the hours to weeks after the initial gamma ray burst, it appears that astronomers have discovered a cosmological imprint made by the burster on its surroundings. This paper discusses the phenomenon of postburst emission in Burst and Transient Source Experiment (BATSE) gamma-ray bursts at energies usually associated with prompt emission. After summing up the background-subtracted signals from hundreds of bursts, it is found that tails out to hundreds of seconds after the trigger could be a common feature of events of a duration greater than 2 seconds, and perhaps of the shorter bursts at a lower and shorter-lived level. The tail component may be softer and seems independent of the duration (within the long-GRB sample) and brightness of the prompt burst emission. Some individual bursts have visible tails at gamma-ray energies, and the spectrum in a few cases differs from that of the prompt emission. For one of these bursts, GRB 991216, afterglow at lower energies was detected, which raised the possibility of seeing afterglow observations over large energy ranges using the next generation of GRB detectors in addition to sensitive space- or ground-based telescopes.
    Keywords: Astronomy
    Type: The Astrophysical Journal; Volume 567; 1028-1036
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  • 24
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    Astrophysics at the Highest Energy Frontiers (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: I discuss recent advances being made in the physics and astrophysics of cosmic rays and cosmic gamma-rays at the highest observed energies as well as the related physics and astrophysics of very high energy cosmic neutrinos. I also discuss the connections between these topics.
    Keywords: Astrophysics
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  • 25
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    Coronal Element Abundances of the Post-Common Envelope Binary V471 Tauri with ASCA (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: We report on ASCA observations of the coronally active companion star in the post-common envelope binary V471 Tau. While it would be prudent to check the following results with grating spectroscopy, we find that a single-temperature plasma model does not fit the data. Two temperature models with variable abundances indicate that Fe is underabundant compared to the Hyades photospheric mean, whereas, the high first ionization potential element Ne is overabundant. This is indicative of the inverse first ionization effect, believed to result from the fractionation of ionized material by the magnetic field in the upper atmosphere of the star. Evolutionary calculations indicate that there should be no peculiar abundances on the companion star resulting from the common envelope epoch. Indeed, we find no evidence for peculiar abundances, although uncertainties are high.
    Keywords: Astrophysics
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  • 26
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    Cryo Cooler Induced Micro-Vibration Disturbances to the Hubble Space Telescope (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: This paper presents an overview of the Hubble Space Telescope (HST) Near Infrared Camera and Multi-Object Spectrometer (NICMOS) Cryo Cooler (MCC) system, a description of the micro-vibration characterization testing performed, and a discussion of the simulated performance. The NCC is a reverse Brayton cycle system that employs micro turbo-machinery to provide cooling to the NICMOS instrument. Extensive testing was conducted to quantify the expected on-orbit disturbances caused by the micro turbo-machinery and provide input to a flexible-body dynamic simulation to demonstrate compliance with the HST 7 milli-arcsecond root mean square jitter requirement.
    Keywords: Astronomy
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  • 27
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    Gravitationally Redshifted Absorption Lines in the Burst Spectra of the Neutron Star in the X-Ray Binary EXO 0748-676 (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: The most straightforward manner of determining masses and radii of neutron stars is by measuring the gravitational redshift of spectral lines produced in the neutron star photosphere; such a measurement would provide direct constraints on the mass-to-radius ratio of the neutron star, and therefore on the equation of state for neutron star matter. Using data taken with the Reflection Grating Spectrometer on board the XMM-Newton observatory we identify, for the first time, significant absorption lines in the spectra of 28 bursts of the low-mass X-ray binary EXO 0748-676. The most significant features are consistent with the Fe XXVI and XXV n=2-3 and O VIII n=1-2 transitions, with a redshift of z=0.35, identical within small uncertainties for the different transitions. This constitutes the first direct and unambiguous measurement of the gravitational redshift in a neutron star.
    Keywords: Astrophysics
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  • 28
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    X-Ray Properties of Lyman Break Galaxies in the Hubble Deep Field North Region (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: We describe the X-ray properties of a large sample of z approximately 3 Lyman Break Galaxies (LBGs) in the region of the Hubble Deep Field North, derived from the 1 Ms public Chandra observation. Of our sample of 148 LBGs, four are detected individually. This immediately gives a measure of the bright AGN (active galactic nuclei) fraction in these galaxies of approximately 3 per cent, which is in agreement with that derived from the UV (ultraviolet) spectra. The X-ray color of the detected sources indicates that they are probably moderately obscured. Stacking of the remainder shows a significant detection (6 sigma) with an average luminosity of 3.5 x 10(exp 41) erg/s per galaxy in the rest frame 2-10 keV band. We have also studied a comparison sample of 95 z approximately 1 "Balmer Break" galaxies. Eight of these are detected directly, with at least two clear AGN based on their high X-ray luminosity and very hard X-ray spectra respectively. The remainder are of relatively low luminosity (〈 10(exp 42) erg/s, and the X-rays could arise from either AGN or rapid star-formation. The X-ray colors and evidence from other wavebands favor the latter interpretation. Excluding the clear AGN, we deduce a mean X-ray luminosity of 6.6 x 10(exp 40) erg/s, a factor approximately 5 lower than the LBGs. The average ratio of the UV and X-ray luminosities of these star forming galaxies L(sub UV)/L (sub X), however, is approximately the same at z = 1 as it is at z = 3. This scaling implies that the X-ray emission follows the current star formation rate, as measured by the UV luminosity. We use our results to constrain the star formation rate at z approximately 3 from an X-ray perspective. Assuming the locally established correlation between X-ray and far-IR (infrared) luminosity, the average inferred star formation rate in each Lyman break galaxy is found to be approximately 60 solar mass/yr, in excellent agreement with the extinction-corrected UV estimates. This provides an external check on the UV estimates of the star formation rates, and on the use of X-ray luminosities to infer these rates in rapidly starforming galaxies at high redshift.
    Keywords: Astrophysics
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    Towards Resolving the Crab Sigma-Problem: A Linear Accelerator? (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: Using the exact solution of the axisymmetric pulsar magnetosphere derived in a previous publication and the conservation laws of the associated MHD flow, we show that the Lorentz factor of the outflowing plasma increases linearly with distance from the light cylinder. Therefore, the ratio of the Poynting to particle energy flux, generically referred to as sigma, decreases inversely proportional to distance, from a large value (typically approx. greater than 10(exp 4)) near the light cylinder to sigma approx. = 1 at a transition distance R(sub trans). Beyond this distance the inertial effects of the outflowing plasma become important and the magnetic field geometry must deviate from the almost monopolar form it attains between R(sub lc), and R(sub trans). We anticipate that this is achieved by collimation of the poloidal field lines toward the rotation axis, ensuring that the magnetic field pressure in the equatorial region will fall-off faster than 1/R(sup 2) (R being the cylindrical radius). This leads both to a value sigma = a(sub s) much less than 1 at the nebular reverse shock at distance R(sub s) (R(sub s) much greater than R(sub trans)) and to a component of the flow perpendicular to the equatorial component, as required by observation. The presence of the strong shock at R = R(sub s) allows for the efficient conversion of kinetic energy into radiation. We speculate that the Crab pulsar is unique in requiring sigma(sub s) approx. = 3 x 10(exp -3) because of its small translational velocity, which allowed for the shock distance R(sub s) to grow to values much greater than R(sub trans).
    Keywords: Astrophysics
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    Is Asteroid 951 Gaspra in a Resonant State with Its Spin Increasing Due to YORP? (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: Asteroid 951 Gaspra appears to be in an obliquity resonance with its spin increasing due to the YORP effect. Gaspra, an asteroid 5.8 km in radius, is a prograde rotator with a rotation period of 7.03 hours. A three million year integration indicates its orbit is stable over at least this time span. From its known shape and spin axis orientation and assuming a uniform density, Gaspra's axial precession period turns out to be nearly commensurate with its orbital precession period, which leads to a resonance condition with consequent huge variations in its obliquity. At the same time its shape is such that the Yarkovsky-O'Keefe-Radzievskii-Paddack effect (YORP effect for short) is increasing its spin rate. The YORP cycle normally leads from spin-up to spin-down and then repeating the cycle; however, it appears possible that resonance trapping can at least temporarily interrupt the YORP cycle, causing spin-up until the resonance is exited. This behavior may partially explain why there is an excess of fast rotators among small asteroids. YORP may also be a reason for small asteroids entering resonances in the first place.
    Keywords: Astrophysics
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    SOFIA's Choice: Scheduling Observations for an Airborne Observatory (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: We describe the problem of scheduling observations for an airborne observatory. The problem is more complex than traditional scheduling problems in that it incorporates complex constraints relating the feasibility of an astronomical observation to the position and time of a mobile observatory, as well as traditional temporal constraints and optimization criteria. We describe the problem, its proposed solution and the empirical validation of that solution.
    Keywords: Astronomy
    Type: 13th International Conference on Artificial Intelligence and Planning and Scheduling; United States
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    Photoevaporation of Clumps in Photodissociation Regions (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: We present the results of an investigation of the effects of Far Ultraviolet (FUV) radiation (6.0eV 〈 hv 〈 13.6eV) from hot early type OB stars on clumps in star-forming molecular clouds. Clumps in FUV-illuminated regions (or photodissociation regions or PDRs) undergo external heating and photodissociation as they are exposed to the FUV field, resulting in a loss of cold, molecular lump mass as it is converted to warm atomic gas. The heating, if rapid, creates strong photoevaporative mass flows off the clump surfaces, and drives shocks into the clumps, compressing them to high densities. The clumps lose mass on relatively short timescales. The evolution of an individual clump is found to be sensitive to three dimensionless parameters: Nc0, the ratio of the initial column density of the clump to the column N(0) approx. 10(exp 21) cm(exp -2) of a warm FUV-heated surface region; upsilon, the ratio of the sound speed in the heated surface to that in the cold clump material: and t(FUV)t(c), the ratio of the "turn-on time" t(FUV) of the heating flux on a clump to its initial sound crossing-time t(c). The evolution also depends on whether a confining interclump medium exists, or whether the interclump region has negligible pressure, as is the case for turbulence-generated clumps. In this paper, we use spherical 1-D numerical hydrodynamic models as well as approximate analytical models to study the dependence of clump photoevaporation on the physical parameters of the clump, and to derive the dynamical evolution, mass loss rates and photoevaporative timescales of a clump for a variety of astrophysical situations. Turbulent clumps evolve so that their column densities are equal to a critical value determined by the local FUV field, and typically have short photo evaporation timescales, approx. 10(exp 4-5) years for a 1 M(solar mass) clump in a typical star-forming region (Nc0 = 10, upsilon = 10). Clumps with insufficient magnetic pressure support, and in strong FUV fields may be driven to collapse by the compressional effect of converging shock waves. We also estimate the rocket effect on photoevaporating clumps and find that it is significant only for the smallest clumps, with sizes much less than the extent of the PDR itself. Clumps that are confined by all interclump medium may either get completely photoevaporated, or may preserve a shielded core with a warm, dissociated, protective shell that, absorbs the incident FUV flux. We compare our results with observations of some well studied PDRs: the Orion Bar, M17SW NGC 2023 and the Rosette Nebula. The data are consistent with both interpretations of clump origin. turbulence and pressure confinement, with a slight indication for favouring the turbulent model for clumps over pressure-confined
    Keywords: Astrophysics
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    The Luminosity Function of QSO Host Galaxies (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: We present some results from our HST archival image study of 71 QSO host galaxies. The objects are selected to have z less than or equal to 0.46 and total absolute magnitude M(sub v) less than or equal to -23 in our adopted cosmology (H(sub 0) = 50 kilometers per second Mpc(sup-1), q(sub 0) = 0.5, lambda = 0)). The aim of this initial study is to investigate the composition of the sample with respect to host morphology and radio loudness, as well as derive the QSO host galaxy luminosity function. We have analyzed available WFPC2 images in R or I band (U in one case), using a uniform set of procedures. The host galaxies span a narrow range of luminosities and are exceptionally bright, much more so than normal galaxies, usually L greater than L*(sub v). The QSOs are almost equally divided among three subclasses: radio-loud QSOs with elliptical hosts, radio-quiet QSOs with elliptical hosts, and radio-quiet QSOs with spiral hosts. Radio-loud QSOs with spiral hosts are extremely rare. Using a weighting procedure, we derive the combined luminosity function of QSO host galaxies. We find that the luminosity function of QSO hosts differs in shape from that of normal galaxies but that they coincide at the highest luminosities. The ratio of the number of quasar hosts to the number of normal galaxies at a luminosity L*(sub v) is R = (Lv/11.48L*(sub v))(sup 2.46), where L*(sub v) corresponds to M*(sub v)= -22.35, and a QSO is defined to be an object with total nuclear plus host light M(sub v) less than or equal to -23. This ratio can be interpreted as the probability that a galaxy with luminosity L(sub V) will host a QSO at redshift z approximately equal to 0.26.
    Keywords: Astrophysics
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    Implications of Ultrahigh Energy Air Showers for Physics and Astrophysics (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: The primary ultrahigh energy particles which produce giant extensive air showers in the Earth atmosphere present an intriguing mystery from two points of view: (1) How are the base particles produced with such astounding energies, eight orders of magnitude higher than those produced by the best man-made terrestrial accelerators? (2) Since they are most likely extragalactic in origin, how do they reach us from extragalactic distances without suffering the severe losses expected from interactions with the 2.7 K thermal cosmic background photons, the so called GZK effect? The answers to these questions may involve new physics: violations of special relativity, grand unification theories, and quantum gravity theories involving large extra dimensions. They may involve new astrophysical sources, "zevatrons". Or some heretofore totally unknown physics or astrophysics may hold the answer. I will discuss here the mysteries involving the production and extragalactic propagation of ultrahigh energy cosmic rays and some suggested possible solutions.
    Keywords: Astrophysics
    Type: 7th Paris Cosmology Colloquium on High Energy Astrophysics for and from Space; United States
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    Thermal and Nonthermal X-ray Emission from the Forward Shock in Tycho's Supernova Remnant (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: We present Chandra CCD images of Tycho's supernova remnant that delineate its outer shock, seen as a thin, smooth rim along the straight northeastern edge and most of the circular western half. The images also show that the Si and S ejecta are highly clumpy, and have reached the forward shock at numerous locations. Most of the X-ray spectra that we examine along the rim show line emission from Si and S, which in some cases must come from ejecta; the continuum is well represented by either thermal or nonthermal models. In the case that the continuum is assumed to be thermal, the temperatures at the rim are all similar at about 2 keV, and the ionization ages are very low because of the overall weakness of the line emission. Assuming shock velocities inferred from radio and X-ray expansion measurements, these temperatures are substantially below those expected for equilibration of the electron and ion temperatures; electron to mean temperature ratios of approximately less than 0.1 - 0.2 indicate at most modest collisionless heating of the electrons at the shock. The nonthermal contribution to these spectra may be important, however, and may account for as many as half of the counts in the 4-6 keV energy range, based on an extrapolation of the hard X-ray spectrum above 10 keV.
    Keywords: Astronomy
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  • 36
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    The Orbit and Position of the X-ray Pulsar XTE J1855-026: An Eclipsing Supergiant System (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: A pulse timing orbit has been obtained for the X-ray binary XTEJ1855-026 using observations made with the Proportional Counter Array on board the Rossi X-ray Timing Explorer. The mass function obtained of approximately 16 solar mass together with the detection of an extended near-total eclipse confirm that the primary star is supergiant as predicted. The orbital eccentricity is found to be very low with a best fit value of 0.04 +/- 0.02. The orbital period is also refined to be 6.0724 +/- 0.0009 days using an improved and extended light curve obtained with RXTE's All Sky Monitor. Observations with the ASCA satellite provide an improved source location of R.A.= 18 hr 55 min 31.3 sec, decl.= -02 deg 36 min 24.0 sec (2000) with an estimated systematic uncertainty of less than 12 min. A serendipitous new source, AX J1855.4-0232, was also discovered during the ASCA observations.
    Keywords: Astrophysics
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    Evidence for a Millisecond Pulsar in 4U 1636-53 During a Superburst (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: We report the discovery with the Proportional Counter Array on board the Rossi X-ray Timing Explorer of highly coherent 582 Hz pulsations during the February 22, 2001 (UT) 'superburst' from 4U 1636-53. The pulsations are detected during an 800 s interval spanning the flux maximum of the burst. Within this interval the barycentric oscillation frequency increases in a monotonic fashion from 581.89 to 581.93 Hz. The predicted orbital motion of the neutron star during this interval is consistent with such an increase as long as optical maximum corresponds roughly with superior conjunction of V801 Arae, the optical companion to the neutron star in 4U 1636-53. We show that a range of circular orbits with 90 〈 v(sub ns) sin i 〈 175 km/s and 0.336 〉 phi(sub 0) 〉 0.277 for the neutron star can provide an excellent description of the frequency and phase evolution. The brevity of the observed pulse train with respect to the 3.8 hour orbital period unfortunately does not allow more precise constraints. The average pulse profile is sinusoidal and the time averaged pulsation amplitude, as inferred from the half amplitude of the sinusoid is 1%, smaller than typical for burst oscillations observed in normal thermonuclear bursts. We do not detect any higher harmonics nor the putative subharmonic near 290 Hz. The 90% upper limits on signal amplitude at the subharmonic and first harmonic are 0.1 and 0.06%, respectively. The highly coherent pulsation, with a Q = v(sub 0)/delta-v 〉 4.5 x 10(exp 5) provides compelling evidence for a rapidly rotating neutron star in 4U 1636-53, and further supports the connection of burst oscillation frequencies with the spin frequencies of neutron stars. Our results provide further evidence that some millisecond pulsars are spun up via accretion in LMXBs. We also discuss the implications of our orbital velocity constraint for the masses of the components of 4U 1636-53.
    Keywords: Astrophysics
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    ATCA Detects Cometary-Shaped Objects In the Giant H II Region (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: Three protoplanetary disks in the giant H II region NGC 3603, originally found by HST (Hubble Space Telescope) + VLT (Very Large Telescope), have been detected with the ATCA (Australia Telescope Compact Array) at 3 and 6 cm. All three ProPlyDs (protoplanetary disks) are clearly resolved, showing a head-tail extent of approx. 4 inches. Proplyd 3 shows the most pronounced head-tail structure with a 3 cm flux density ratio between head and tail of about 10:1. The tail is very well defined and at least 2 inches long, pointing away from the central star cluster. Unfortunately, ProPlyD 3 is rather faint in the low-sensitivity HST broad band image shown by Brandner et al.; it is located outside the region of their high sensitivity HST H(alpha) image.
    Keywords: Astrophysics
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    Chandra Observations of the Evening Core of the Starburst Galaxy NGC 253 (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: Chandra observations of the core of the nearby starburst galaxy NGC 253 reveal a heavily absorbed source of hard X-rays embedded within the nuclear starburst region. The source has an unabsorbed, 2 to 10 keV luminosity of greater than or equal to 10(exp 39) erg per s and photoionizes the surrounding gas. We observe this source through a dusty torus with a neutral absorbing column density of N(sub eta) approximately 2 x 10(exp 23)cm (exp -2). The torus is hundreds of pc across and collimates the starburst-driven nuclear outflow. We suggest that the ionizing source is an intermediate-mass black hole or a weakly accreting supermassive black hole, which may signal the beginnings or endings of AGN (active galactic nuclei) activity.
    Keywords: Astrophysics
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  • 40
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    The Spin Pulse of the Intermediate Polar V1062 Tauri (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: We combine ASCA and RXTE data of V1062 Tau to confirm the presence of a 62-min X-ray pulsation. We show that the pulsation is caused largely by the variation of dense partial absorption, in keeping with current models of accretion onto magnetic white dwarfs. Further parameterisation of the spin pulse is, however, hampered by ambiguities in the models.
    Keywords: Astrophysics
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    Chandra Observation of Luminous and Ultraluminous X-ray Binaries in M101 (2002)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: X-ray binaries in the Milky Way are among the brightest objects on the X-ray sky. With the increasing sensitivity of recent missions, it is now possible to study X-ray binaries in nearby galaxies. We present data on six ultraluminous binaries in the nearby spiral galaxy, M101, obtained with Chandra ACIS-S. Of these, five appear to be similar to ultraluminous sources in other galaxies, while the brightest source, P098, shows some unique characteristics. We present our interpretation of the data in terms of an optically thick outflow, and discuss implications.
    Keywords: Astrophysics
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  • 42
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    An X-ray Investigation of the NGC 346 Field (2002)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: We present results from a Chandra observation of the NGC 346 star formation region, which contains numerous massive stars, and is related to N66, the largest H(II) region of the SMC (Small Magellanic Cloud). In this first paper, we will focus on the characteristics of the main objects of the field. The NGC 346 cluster itself shows only relatively faint X-ray emission (with L((sub X)(sup unabs)) is approximately 1.5 x 10(exp 34) erg s(exp -1), tightly correlated with the core of the cluster. In the field also lies HD 5980, a LBV (Luminous Blue Variable) star in a binary (or triple system) that is detected for the first time at X-ray energies. The star is X-ray bright, with an unabsorbed luminosity of L((sub X)(sup unabs)) is approximately 1.7 x 10(exp 34) erg s(exp -1), but needs to be monitored further to investigate its X-ray variability over a complete orbital cycle. The high X-ray luminosity may be associated either with colliding winds in the binary system or with the 1994 eruption. HD 5980 is surrounded by a region of diffuse X-ray emission, which may be a superimposed supernova remnant.
    Keywords: Astronomy
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  • 43
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    Production and Performance of the InFOCmicronS 20-40 keV Graded Multilayer Mirror (2002)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: The International Focusing Optics Collaboration for micron Crab Sensitivity (InFOC micronS) balloon-borne hard x-ray incorporates graded multilayer technology to obtain significant effective area at energies previously inaccessible to x-ray optics. The telescope mirror consists of 2040 segmented thin aluminum foils coated with replicated Pt/C multilayers. A sample of these foils was scanned using a pencil-beam reflectometer to determine, multilayer quality. The results of the reflectometer measurements demonstrate our capability to produce large quantity of foils while maintaining high-quality multilayers with a mean Nevot-Croce interface roughness of 0.5nm. We characterize the performance of the complete InFOC micronS telescope with a pencil beam raster scan to determine the effective area and encircled energy function of the telescope. The effective area of the complete telescope is 78, 42 and 22 square centimeters at 20 30 and 40 keV. respectively. The measured encircled energy fraction of the mirror has a half-power diameter of 2.0 plus or minus 0.5 arcmin (90% confidence). The mirror successfully obtained an image of the accreting black hole Cygnus X-1 during a balloon flight in July, 2001. The successful completion and flight test of this telescope demonstrates that graded-multilayer telescopes can be manufactured with high reliability for future x-ray telescope missions such as Constellation-X.
    Keywords: Astronomy
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  • 44
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    Burst Oscillation Periods from 4U 1636-53: A Constraint on the Binary Doppler Modulation (2002)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: The burst oscillations seen during Type 1 X-ray bursts from low mass X-ray binaries (LMXB) typically evolve in period towards an asymptotic limit that likely reflects the spin of the underlying neutron star. If the underlying period is stable enough, measurement of it at different orbital phases may allow a detection of the Doppler modulation caused by the motion of the neutron star with respect to the center of mass of the binary system. Testing this hypothesis requires enough X-ray bursts and an accurate optical ephemeris to determine the binary phases at which they occurred. We present here a study of the distribution of asymptotic burst oscillation periods for a sample of 26 bursts from 4U 1636-53 observed with the Rossi X-ray Timing Explorer (RXTE). The burst sample includes both archival and proprietary data and spans more than 4.5 years. We also present new optical light curves of V801 Arae, the optical counterpart of 4U 1636-53, obtained during 1998-2001. We use these optical data to refine the binary period measured by Augusteijn et al. to 3.7931206(152) hours. We show that a subset of approx. 70% of the bursts form a tightly clustered distribution of asymptotic periods consistent with a period stability of approx. 1 x 10(exp -4). The tightness of this distribution, made up of bursts spanning more than 4 years in time, suggests that the underlying period is highly stable, with a time to change the period of approx. 3 x 10(exp 4) yr. This is comparable to similar numbers derived for X-ray pulsars. We investigate the period and orbital phase data for our burst sample and show that it is consistent with binary motion of the neutron star with v(sub ns) sin i 〈 38 and 50 km/s at 90 and 99% confidence, respectively. We use this limit as well as previous radial velocity data to constrain the binary geometry and component masses in 4U 1636-53. Our results suggest that unless the neutron star is significantly more massive than 1.4 solar masses the secondary is unlikely to have a mass as large as 0.36 solar masses, the mass estimated assuming it is a main sequence star which fills its Roche lobe. We show that a factor of 3 increase in the number of bursts with asymptotic period measurements should allow a detection of the neutron star velocity.
    Keywords: Astrophysics
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  • 45
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    Intercontinental Bistatic Radar Test Observation of Asteroid 1998 WT24 (2002)
    In:  Other Sources
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    Publication Date: 2011-08-23
    Description: We describe the first intercontinental planetary radar test performed in Italy observing the near Earth asteroid (NEA) 33342 (1998 WT24) in December 2001 by means of the bistatic configurations Goldstone (California, USA)-Medicina (Italy) and Evpatoria (Ukraine)-Medicina. The experiment goal was to characterize the system for realtime radar follow-up observations of NEAs and artificial orbiting debris, in the framework of a feasibility study which aims at using the Sardinia Radio Telescope, at present under construction, also as a planetary radar facility. We report the preliminary results of the radar observations carried out by the IRA-CNR (Instituto di Radioastronomia - Consiglio Nazionale delle Ricerche) and the OATo (Osservatorio Astronomico di Torino) groups, aimed at exploring the scientific potentials of a new space radar program, using the existing facilities in Italy. The planetary radar technique is uniquely capable of investigating geometry and surface properties of various solar system objects, demonstrating advantages over the optical methods in its high spatial resolution and ability to obtain three-dimensional images. A single radar detection allows to obtain extremely accurate orbital elements, improving the instantaneous positional uncertainties by orders of magnitude with respect to an optically determined orbit. Radar is a powerful means to spatially resolve NEAs by measuring the distribution of the echo power in time delay (range) and Doppler frequency (line-of-sight velocity) with extreme precision in each coordinate, as it provides detailed information about the target physical properties like size, shape, rotation, near-surface bulk density and roughness and internal density distribution. The Medicina 32m antenna had been successfully used for the first time as the receiving part of a bistatic configuration during a test experiment (September 2001) held to check the capabilities of the entire data acquisition system. This test was possible thanks to the collaboration undertaken with the Evpatoria radar station, and consisted in the observation of the ETALON-1 low orbit satellite
    Keywords: Astrophysics
    Type: Solar System Remote Sensing; 65; LPI-Contrib-1129
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  • 46
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    On Overview of the Performance and Scientific Results from the Chandra X-Ray Observatory (2002)
    In:  Other Sources
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    Publication Date: 2011-08-23
    Description: The Chandra X-Ray Observatory (CXO) was launched on 1999 July 23 by the Columbia Space Shuttle. The first X-rays focused by the telescope were seen on 1999 August 12 after the satellite systems were activated. Beginning with the first observation, it was clear that the telescope was not damaged by the launch environment and was operating as planned. After the early surprise due to the discovery that the telescope concentrated CCD-damaging low-energy protons far more efficiently than had been expected, the observatory is performing optimally and is returning excellent scientific data. Together with other space observatories, especially XMM-Newton, it is obvious that we have entered a new era of discovery in high-energy astrophysics.
    Keywords: Astronomy
    Type: Publications of the Astronomical Society of the Pacific; Volume 114; 1-24
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  • 47
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    The Development of a Data Archive and Analysis Tools for WIRE (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: Although a number of missions to perform asteroseismology from orbit are planned, such as the French COROT (currently scheduled for launch in 2004), the Canadian MOST (2002), and the Danish MONS (2003), none has yet been successfully flown. However, from May 1999 through September 2000, the PI of this proposal initiated a program using the star camera on board the WIRE spacecraft to perform high-precision photometry of solar-like and giant stars. This program relied on the on-board star camera, which consists of a 50mm f/1.75 telescope feeding a 512(sup 2) SITe CCD, which can be read out at rates as high as 10 Hz. The high cadence of observations available with this star camera is made possible by software that locates the 5 brightest stars in the field and reads only an 8x8 pixel box around one selected image. An additional mode of operation, available since November 1999, makes count rate data available on all five stellar images, with a consequent loss of read rate (to 2 Hz for 5 stars). Stellar images are defocused (to allow for more accurate image centroiding), but the entire stellar image lies within the 64-pixel box. we note that in many ways, this instrument is similar to the French instrument EVRIS, which was intended to perform asteroseismology with a 90 mm telescope, but which unfortunately flew as part of the failed Russian MARS 96 spacecraft.
    Keywords: Astronomy
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  • 48
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    An ISO and IUE Study of Planetary Nebula NGC 2440 (2002)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: The infrared and ultraviolet spectra of planetary nebula NGC 2440 is presented. The observations were made respectively by the Infrared Space Observatory (ISO) and International Ultraviolet Explorer (IUE) These data, in conjunction with published optical observations have been used to derive electron temperature and density. A trend of electron temperature with ionization potential is found. In particular the electron temperature increases from 11000 to 18000 K with increasing IBM. The electron density has a constant value of 4500/cu cm in agreement with previous determination. The chemical abundance has been derived for the following elements; helium, carbon, nitrogen, oxygen, neon, sulfur and argon. The ionization correction factor turns out to be very small (almost unnecessary) for all species except sulfur.
    Keywords: Astrophysics
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    Abundances of Planetary Nebula NGC 5315 (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: The ISO and IUE spectra of the elliptical nebula NGC 5315 is presented. These spectra axe combined with the spectra in the visual wavelength region to obtain a complete, extinction corrected, spectrum. The chemical composition of the nebulae is then calculated and compared to previous determinations. The HST Nicmos observations of the nebula in 3 emission lines are also presented. These observations are used to determine the helium abundance as a function of position in the nebula. A discussion is given of possible evolutionary effects.
    Keywords: Astrophysics
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  • 50
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    Overview of the Chandra X-Ray Observatory Facility (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: The Chandra X-Ray Observatory (originally called the Advanced X-Ray Astrophysics Facility - AXAF) is the X-Ray component of NASA's "Great Observatory" Program. Chandra is a NASA facility that provides scientific data to the international astronomical community in response to scientific proposals for its use. The Observatory is the product of the efforts of many organizations in the United States and Europe. The Great Observatories also include the Hubble Space Telescope for space-based observations of astronomical objects primarily in the visible portion of the electromagnetic spectrum, the now defunct Compton Gamma- Ray Observatory that was designed to observe gamma-ray emission from astronomical objects, and the soon-to-be-launched Space Infrared Telescope Facility (SIRTF). The Chandra X-Ray Observatory (hereafter CXO) is sensitive to X-rays in the energy range from below 0.1 to above 10.0 keV corresponding to wavelengths from 12 to 0.12 nanometers. The relationship among the various parts of the electromagnetic spectrum, sorted by characteristic temperature and the corresponding wavelength, is illustrated. The German physicist Wilhelm Roentgen discovered what he thought was a new form of radiation in 1895. He called it X-radiation to summarize its properties. The radiation had the ability to pass through many materials that easily absorb visible light and to free electrons from atoms. We now know that X-rays are nothing more than light (electromagnetic radiation) but at high energies. Light has been given many names: radio waves, microwaves, infrared, visible, ultraviolet, X-ray and gamma radiation are all different forms. Radio waves are composed of low energy particles of light (photons). Optical photons - the only photons perceived by the human eye - are a million times more energetic than the typical radio photon, whereas the energies of X-ray photons range from hundreds to thousands of times higher than that of optical photons. Very low temperature systems (hundreds of degrees below zero Celsius) produce low energy radio and microwave photons, whereas cool bodies like our own (about 30 degrees Celsius) produce infrared radiation. Very high temperatures (millions of degrees Celsius) are one way of producing X-rays.
    Keywords: Astronomy
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    Formation Flying Satellite Control Around the L2 Sun-Earth Libration Point (2002)
    In:  CASI
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    Publication Date: 2013-08-29
    Description: This paper discusses the development of a linear control algorithm for formations in the vicinity of the L2 sun-Earth libration point. The development of a simplified extended Kalman filter is included as well. Simulations are created for the analysis of the stationkeeping and various formation maneuvers of the Stellar Imager mission. The simulations provide tracking error, estimation error, and control effort results. For formation maneuvering, the formation spacecraft track to within 4 meters of their desired position and within 1.5 millimeters per second of their desired zero velocity. The filter, with few exceptions, keeps the estimation errors within their three-sigma values. Without noise, the controller performs extremely well, with the formation spacecraft tracking to within several micrometers. Each spacecraft uses around 1 to 2 grams of propellant per maneuver, depending on the circumstances.
    Keywords: Astrophysics
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  • 52
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    Binary black holes, accretion disks and relativistic jets: photocenters of nearby AGN and quasars (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astrophysics
    Type: American Astronomical Society 199th Meeting; Washington, DC; United States
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    Exceptional stars origins, companions, masses and planets (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: American Astronomical Society 199th Meeting; Washington, DC; United States
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  • 54
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    Proper motions in the knotty bipolar jet in Hen 2-90 (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: Using second-epoch HST imaging of the unusual, bipolar jet source Hen 2-90, we have discovered proper motions of 0.03 arcsec yr-1 in the jet knots.
    Keywords: Astrophysics
    Type: Astrophysical Journal
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  • 55
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    SAFIR web site (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
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  • 56
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    The spectral correlation of functional clouds: a statistical test for theoretical models (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We compute the spectral correlation function (SCF) of CO J=1-0 maps of moleculary cloud complexes. The SCF is a power law over approximately an order of magnitude in spatial separation in every map. The power law slope of the SCF, its normalization, and the spectral line width averaged over the whole map, are computed for all the observational maps.
    Keywords: Astrophysics
    Type: Astrophysical Journal
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  • 57
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    The x-ray luminosities of Herbig-Haro objects (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We find that our analytic model reproduces the observed X-ray luminosity of HH 2, and we propose that HH 80/81 is a good candidate for future observations with Chandra.
    Keywords: Astrophysics
    Type: Astrophysical Journal Letters
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  • 58
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    Massive stars and the energy balance of the ISM: I. The imapct of an isolated 60 M star (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We present results of numerical simulations carried out with a 2D radiation hydrodynamics code in order to study the impact of massive stars on their surrounding interstellar medium. This first paper deals with the evolution of the circumstellar gas around an isolated 60 M star.
    Keywords: Astrophysics
    Type: Astrophysical Journal
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  • 59
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    Black holes: feeling the ripples (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Space Place: a column for amature astronomy club members
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  • 60
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    Companions to isolated elliptical galaxies: revisiting the Bothun-Sullivan (1977) sample using the NASA/IPAC extragalactic database (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We investigate the number of physical companion galaxies for a sample of relatively isolated elliptical galaxies. The NASA/IPAC Extragalactic Database (NED) has been usedto reinvestigate the incidence of satellite galaxies for a sample of 34 elliptical galaxies, firstinvestigated by Bothun & Sullivan (1977) using a visual inspection of Palomar Sky Survey prints out to a projected search radius of 75 kpc. We have repeated their original investigation usingdata cataloged data in NED. Nine of these ellipticals appear to be members of galaxy clusters:the remaining sample of 25 galaxies reveals an average of +1.0 f 0.5 apparent companions per galaxy within a projected search radius of 75 kpc, in excess of two equal-area comparisonregions displaced by 150-300 kpc. This is nearly an order of magnitude larger than the +0.12+/- 0.42 companions/galaxy found by Bothun & Sullivan for the identical sample. Making use of published radial velocities, mostly available since the completion of the Bothun-Sullivan study,identifies the physical companions and gives a somewhat lower estimate of +0.4 companions per elliptical. This is still a factor of 3x larger than the original statistical study, but giventhe incomplete and heterogeneous nature of the survey redshifts in NED, it still yields a firmlower limit on the number (and identity) of physical companions. An expansion of the searchradius out to 300 kpc, again restricted to sampling only those objects with known redshifts in NED, gives another lower limit of 4.3 physical companions per galaxy. (Excluding fiveelliptical galaxies in the Fornax cluster this average drops to 3.5 companions per elliptical.)These physical companions are individually identified and listed, and the ensemble-averagedradial density distribution of these associated galaxies is presented. For the ensemble, the radial density distribution is found to have a fall-off consistent with p c( R^-0.5 out to approximately150 kpc. For non-Fornax cluster companions the fall-off continues out to the 300-kpc limit of thesurvey. The velocity dispersion of these companions is found to be constant with projected radial distance from the central elliptical, holding at a value of approximately +/- 300-350 km/sec overall.
    Keywords: Astrophysics
    Type: Astrophysical Journal
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    Runaway fragmentation of sungrazing comets observed with the solar and heliospheric observatory (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: The strong propensity of the SOHO sungrazing comets for clustering is a product of their runaway fragmentation throughout the orbit about the Sun.
    Keywords: Astrophysics
    Type: Astrophysical Journal
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    Experimental study of SubMM wave superconducting hot-electron direct detectors (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astrophysics
    Type: Applied Superconductivity Conference 2002; Houston, TX; United States
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  • 63
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    ROSAT/ASCA observations of the mixed-morphology supernova remnant W28 (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We present three sets of ROSAT PSPC and four sets of ASCA observations of the supernova remnant (SNR) W28. The overall shape of x-ray emission in W28 is elliptical, dominated by a centrally-concentrated interior emission, sharply peaked at the center. There are also partial northeastern and southwestern shells, and both central and shell x-ray emission is highly patchy.
    Keywords: Astrophysics
    Type: The Astrophysical Journal
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  • 64
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    Multi-color interferometric observations of Mira stars (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: Interferometric observations in the atmospheric windows of the near infrared (1 to 4 microns) can be efficiently used to probe the chemical composition of Miras atmosphere and provide direct measurements of extended gas layers around these stars. This is illustrated by recent Miras observations carried out with the FLUOR instrument of the IOTA interferometer (Mennesson et al. 2002, and Perrin et al. proceedings of this conference) and with the PTI test-bed (Thompson 2002, Thompson et al. 2002). These visibility measurements show evidence for continuum emission from very extended ( 2-3 stellar radii) semi-transparent gaseous atmospheric layers, and large apparent diameter changes with pulsation phase. Interestingly these observations are consistent with the extended molecular gas layers (H20, CO ...) already inferred around some of these objects from IS0 and high resolution ground-based FTS infrared spectra.
    Keywords: Astronomy
    Type: Mass-Losing Pulsating Stars and Their Circumstellar Matter; Sendai; Japan
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  • 65
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    On the predominance of the radial component of the magnetic field in the solar corona (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: In this paper, the polarized intensity measurements of the Fe XIII 10747 A line described by Arnaud are placed, for the first time, in the context of the corresponding pB images from the HAO Mauna Loa MkIII K-Coronameter, which first became available in 1980. It is shown how the predominance of the radial direction of the coronal magnetic field at solar maximum is consistent with radially expanding magnetic field lines coexisting with the large-scale structures associated with streamers.
    Keywords: Astrophysics
    Type: Astrophysical Journal
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    Black holes: felling the ripples (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Space place column for amateur astronomy club partner newsletters
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  • 67
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    X-ray synchronization emitting Fe-rich ejecta in SNR RCW 86 (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: Supernova remnants may exhibit both thermal and nonthermal X-ray emission. In a previous study with ASCA data, we found that the middle-aged supernova remnant RCW 86 showed evidence for both processes, and predicted that observations with much higher spatial resolution would distinguish harder X-rays, which we proposed were primarily synchrotron emission, from softer, thermal X-rays. Here we describe Chandra observations which amply confirm our predictions.
    Keywords: Astrophysics
    Type: Astrophysical Journal
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    The optical polarization of near-infrared selected QSOs (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: Optical broad-band polarimetry is presented for near-infrared color-selected active galactic nuclei (AGN) classified as quasi-stellar objects (QSOs) based on their Ks-band luminosity.
    Keywords: Astrophysics
    Type: The Astrophysical Journal
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  • 69
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    Angular size measurements of Mira variable stars at 2.2 mu m. II (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We present angular size measurements of 22 oxygen-rich Mira variable stars.
    Keywords: Astronomy
    Type: Astronomical Journal
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  • 70
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    X-ray counts and contribution to the XRB of an IR selected sample of starburst and active galaxies (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: X-ray Surveys, in the Light of New Observatories; Satander; Spain
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  • 71
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    Resolving starforming regions in distant galaxies: Blue Spheroid Candidates out at z 〈 1 (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Hubble's Science Legacy: Future Optical-UV Astronomy from Space Workshop; Chicago, IL; United States
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  • 72
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    Warm dust around main-sequence stars discovered with 2MASS (2002)
    In:  Other Sources
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    Publication Date: 2018-06-11
    Description: We report results of ground-based 10 mu m photometry of main-sequence stars with warm circumstellar dust.
    Keywords: Astronomy
    Type: Symposium on Debris Disks and Planet Formation; Tucson, AZ; United States
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  • 73
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    HERO (Hyper Extremely Red Object) in the field near 53W002 (2002)
    In:  Other Sources
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    Publication Date: 2018-06-11
    Description: HERO's are objects which are very red in NIR colors. We report the discovery of a HERO in the field which includes a known radio galaxy, 53WOO2, and a possible cluster of glaxies both at z = 2.39.
    Keywords: Astrophysics
    Type: Astrophysical Journal Letters
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    Condensation Processes in Astrophysical Environments (2002)
    In:  CASI
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    Publication Date: 2018-06-06
    Description: Astrophysical systems present an intriguing set of challenges for laboratory chemists. Chemistry occurs in regions considered an excellent vacuum by laboratory standards and at temperatures that would vaporize laboratory equipment. Outflows around Asymptotic Giant Branch (AGB) stars have timescales ranging from seconds to weeks depending on the distance of the region of interest from the star and, on the way significant changes in the state variables are defined. The atmospheres in normal stars may only change significantly on several billion-year timescales. Most laboratory experiments carried out to understand astrophysical processes are not done at conditions that perfectly match the natural suite of state variables or timescales appropriate for natural conditions. Experimenters must make use of simple analog experiments that place limits on the behavior of natural systems, often extrapolating to lower-pressure and/or higher-temperature environments. Nevertheless, we argue that well-conceived experiments will often provide insights into astrophysical processes that are impossible to obtain through models or observations. This is especially true for complex chemical phenomena such as the formation and metamorphism of refractory grains under a range of astrophysical conditions. Data obtained in our laboratory has been surprising in numerous ways, ranging from the composition of the condensates to the thermal evolution of their spectral properties. None of this information could have been predicted from first principals and would not have been credible even if it had.
    Keywords: Astrophysics
    Type: Proceedings of the NASA Laboratory Astrophysics Workshop; 213-216; NASA/CP-2002-211863
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    Laboratory Studies of the Optical Properties and Condensation Processes of Cosmic Dust Grains (2002)
    In:  CASI
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    Publication Date: 2018-06-06
    Description: A laboratory facility for conducting a variety of experiments on single isolated dust particles of astrophysical interest levitated in an electrodynamics balance has been developed at NASA/Marshall Space Flight Center. The objective of the research is to employ this experimental technique for studies of the physical and optical properties of individual cosmic dust grains of 0.1-100 micron size in controlled pressure/temperatures environments simulating astrophysical conditions. The physical and optical properties of the analogs of interstellar and interplanetary dust grains of known composition and size distribution will be investigated by this facility. In particular, we will carry out three classes of experiments to study the micro-physics of cosmic dust grains. (1) Charge characteristics of micron size single dust grains to determine the photoelectric efficiencies, yields, and equilibrium potentials when exposed to UV radiation. (2) Infrared optical properties of dust particles (extinction coefficients and scattering phase functions) in the 1-30 micron region using infrared diode lasers and measuring the scattered radiation. (3) Condensation experiments to investigate the condensation of volatile gases on colder nucleated particles in dense interstellar clouds and lower planetary atmospheres. The condensation experiments will involve levitated nucleus dust grains of known composition and initial mass (or m/q ratio), cooled to a temperature and pressure (or scaled pressure) simulating the astrophysical conditions, and injection of a volatile gas at a higher temperature from a controlled port. The increase in the mass due to condensation on the particle will be monitored as a function of the dust particle temperature and the partial pressure of the injected volatile gas. The measured data will permit determination of the sticking coefficients of volatile gases and growth rates of dust particles of astrophysical interest. Some preliminary results based on measurements of photoelectric emission and radiation pressure on single isolated 0.2 to 6.6 micron size silica particles exposed to UV radiation at 120-200 nm and green laser light at 532 nm are presented.
    Keywords: Astrophysics
    Type: Proceedings of the NASA Laboratory Astrophysics Workshop; 180-184; NASA/CP-2002-211863
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    The Laboratory Production of Complex Organic Molecules in Simulated Interstellar Ices (2002)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: Much of the volatiles in interstellar dense clouds exist in ices surrounding dust grains. Their low temperatures preclude most chemical reactions, but ionizing radiation can drive reactions that produce a suite of new species, many of which are complex organics. The Astrochemistry Lab at NASA Ames studies the UV radiation processing of interstellar ice analogs to better identify the resulting products and establish links between interstellar chemistry, the organics in meteorites, and the origin of life on Earth. Once identified, the spectral properties of the products can be quantified to assist with the search for these species in space. Of particular interest are findings that UV irradiation of interstellar ice analogs produces molecules of importance in current living organisms, including quinones, amphiphiles, and amino acids.
    Keywords: Astrophysics
    Type: Proceedings of the NASA Laboratory Astrophysics Workshop; 198-200; NASA/CP-2002-211863
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    Laboratory Measurements of Solar-Wind/Comet X-Ray Emission and Charge Exchange Cross Sections (2002)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: The detection of X-rays from comets such as Hyakutake, Hale-Bopp, d Arrest, and Linear as they approach the Sun has been unexpected and exciting. This phenomenon, moreover, should be quite general, occurring wherever a fast solar or stellar wind interacts with neutrals in a comet, a planetary atmosphere, or a circumstellar cloud. The process is, O(+8) + H2O --〉 O(+7*) + H2O(+), where the excited O(+7*) ions are the source of the X-ray emissions. Detailed modeling has been carried out of X-ray emissions in charge-transfer collisions of heavy solar-wind Highly Charged Ions (HCIs) and interstellar/interplanetary neutral clouds. In the interplanetary medium the solar wind ions, including protons, can charge exchange with interstellar H and He. This can give rise to a soft X-ray background that could be correlated with the long-term enhancements seen in the low-energy X-ray spectrum of ROSAT. Approximately 40% of the soft X-ray background detected by Exosat, ROSAT, Chandra, etc. is due to Charge Exchange (CXE): our whole heliosphere is glowing in the soft X-ray due to CXE.
    Keywords: Astrophysics
    Type: Proceedings of the NASA Laboratory Astrophysics Workshop; 117-119; NASA/CP-2002-211863
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    Surveying the solar neighborhood for brown dwarf companions with the ECLIPSE Discovery mission (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Brown Dwarfs - International Astronomical Union Symposisum; Waikoloa, HI; United States
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    Recent results for solar-system tests of general relativity (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astrophysics
    Type: 200th AAS Meeting; Albuquerque, NM; United States
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    Prospecting for brown dwarfs in Space Infrared Telescope Facility (SIRTF) legacy science datasets (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Brown Dwarfs International Astronomical Union (IAU) Symposium; Kona, HI; United States
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    Rotation of intermediate and low mass MS stars (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Stellar Rotation/ International Astronomical Union (IAU) Symposium No. 215; Cancun; Mexico
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    On the relationship between stellar rotation and radius in young clusters (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We examine the early angular momentum history of stars in young clusters. We reported based on 197 photometric periods in the Orion Flanking Fields and 83 photometric periods in the NGC 2264, that PMS stars apparently do not conserve stellar angular momentum as they evolve down their connective tracks, but instead evolve at nearly constant angular velocity.
    Keywords: Astronomy
    Type: AAS 200th Meeting; Albuquerque, NM; United States
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    An attitude control system for the SIM Interferometry Test Bed 3 (STB3) (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: AS 05: Astronomy with Large Telescopes: Interferometery for Optical Astronomy II; Waikoloa, HI; United States
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    Science overview of the SIM project (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Astronomical Telescopes and Instrumentation; Waikoloa, HI; United States
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    Education and public outreach at the SIRTF science center (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: Communicating the world of infrared astronomy to the public is the main vocation of the Education and Public Outreach Office of the SIRTF Science Center; but certainly not its only goal. In the past few years we have created a wide variety of educational products that explains the infrared as well as the multi-wavelength universe.
    Keywords: Astronomy
    Type: International Astronomical Union Symposium 213: Bioastronomy 2002: Life Among the Stars; Australia
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    Preliminary performance measurements of bolometers for the planck high frequency instrument (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We report on the characterization of bolometers fabricated at the Jet Propulsion Laboratory for the High Frequency Instrument (HFI) of the joint ESA/NASA Herschel/Planck mission to be launched in 2007.
    Keywords: Astronomy
    Type: International Society for Optical Engineering (SPIE) Astronomical Telescopes and Instrumentation; Waikoloa, HI; United States|Proceedings of the SPIE Astronomical Telescopes and Instrumentation
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    Bolometric detectors for the Planck surveyor (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: The High Frequency Instrument on the NASA/ESA Planck Surveyor, scheduled for launch in 2007, will map the entire sky in 6 frequency bands ranging from 100 GHz to 857 GHz to probe Cosmic Microwave Background (CMB) anisotropy and polarization with angular resolution ranging from 9' to 5'. The HFI focal plane will contain 48 silicon nitride micromesh bolometers operating from a 100 mK heat sink. Four detectors in each of the 6 bands will detect unpolarized radiation. An additional 4 pairs of detectors will provide sensitivity to linear polarization of emission at 143, 217 and 353 GHz. We report on the development and characterization of these detectors before delivery to the European HFI consortium.
    Keywords: Astronomy
    Type: Proceedings of SPIE, Millimeter and Submillimeter Detectors for Astronomy|SPIE, Millimeter and Submillimeter Detectors for Astronomy; Waikoloa, HI; United States
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    The search for complex hydrocarbons and biogenic molecules using rotational transitions from radio to millimeter wavelengths (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: International Astronomical Union (IAU) Symposium 213 Bioastronomy 2002: Life Among the Stars; Hamilton Island; Australia
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    Finding calibrator stars (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: EuroWinter School Observing with the Very Large Telescope Interferometer; Les Houches; France
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    Speckle holographic imaging of pre-main sequence visual binaries in Taurus (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: 199th Meeting of the American Astronomical Society; Washington, DC; United States
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    Phasor averaging analysis on cyclic errors (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: 199th Meeting of the American Astronomical Society; Washington, DC; United States
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    Simulations of effects of vibration and pathlength modulation errors on the accuracy of SIM delay measurements (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: 199th Meeting of the American Astronomical Society; Washington, DC; United States
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    Structure of the inner region of T Tauri circumstellar disks (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: 199th Meeting of the American Astronomical Society; Washington, DC; United States
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    The square kilometer array: what it means for planetary science (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: The radio astronomy community has begun work on a radio telescpe with a square kilometer of connecting area- the Square Kilometer Array (SKA).
    Keywords: Astronomy
    Type: Division for Planetary Sciences Meeting of the American Astronomical Society; New Orleans, LA; United States
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    Infall and the accretion shock in the protostellar disk: L1157 (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: 199th American Astronomical Society Meeting; Washington, DC; United States
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    The square kilometer array as a spacecraft tracking facility (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: American Astronomical Society; Washington, DC; United States
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    Chemical tracers of interstellar turbulence (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: 76th UCL Astronomy Colloquium; Windsor; United Kingdom
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    Error analysis of photometry in SIM (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: 200th Meeting of the American Astronomical Society; Albuquerque, NM; United States
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    Warm dust around main-sequence stars discovered with 2MASS (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Astronomy
    Type: Fred Gillett Symposium on Debris Disks and Planet Formation; Tucson, AZ; United States
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    Overview of SIM wide angle astrometric system calibration strategies (2002)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: This paper summarizes two very different strategies envisioned for calibrating the systematic field dependent biases present in the Space Interferometry Mission (SIM) instrument. The Internal Calibration strategy is based on pre-launch measurements combined with a set of on orbit measurements generated by a source internal to the instrument. The External Calibration strategy uses stars as an external source for generating the calibration function. Both approaches demand a significant amount of innovation given that SIM's calibration strategy requires a post-calibration error of 100picometers over a 15 degree field of regard while the uncalibrated instrument introduces 10's-100's of nanometers of error. The calibration strategies are discussed in the context of the Wide Angle Astrometric mode of the instrument, although variations on the Internal Calibration Strategy may be used for doing Narrow Angle Astrometry.
    Keywords: Astronomy
    Type: Astronomical Telescopes and Instrumentation Conference; Waikoloa, HI; United States
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