SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS
A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 44, ISSUE 10 - MAY 19, 2006
90 ASTROPHYSICS
Includes cosmology; celestial mechanics; space plasmas; and interstellar and interplanetary gases and dust.
20060012259 NASA Goddard Space Flight Center, Greenbelt, MD, USA
GLAST Large Area Telescope Multiwavelength Planning
Thompson, D. J.; Cameron, R. A.; Digel, S.W.;Wood, K. S.; January 2006; 1 pp.; In English; American Astronomical Society 207th Meeting, 8-12 Jan. 2006, Washington, DC, USA; No Copyright; Avail.: Other Sources; Abstract Only
Because gamma-ray astrophysics depends in many ways on multiwavelength studies, the GLAST Large Area Telescope (LAT) Collaboration has started multiwavelength planning well before the scheduled 2007 launch of the observatory. Some of the high-priority needs include: (1) radio and X-ray timing of pulsars; (2) expansion of blazar catalogs, including redshift measurements (3) improved observations of molecular clouds, especially at high galactic latitudes; (4) simultaneous broad-spectrum blazar flare measurements; (5) characterization of gamma-ray transients, including gamma ray bursts; (6) radio, optical, X-ray and TeV counterpart searches for unidentified gamma-ray sources. Work on the first three of these activities is needed before launch. The GLAST Large Area Telescope is an international effort, with U.S. funding provided by the Department of Energy and NASA. Author
Gamma Ray Bursts; Blazars; Telescopes; Molecular Clouds; Gamma Rays; Astrophysics; Spectral Counterparts (Astronomy)
20060012283 NASA Goddard Space Flight Center, Greenbelt, MD, USA
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Physical Conditions of Eta Car Complex Environment Revealed From Photoionization Modeling
Verner, E. M.; Bruhweiler, F.; Nielsen, K. E.; Gull, T.; Kober, G. Vieira; Corcoran, M.; Bulletin of the American Astronomical Society; [2006]; Volume 37, No. 4; 1 pp.; In English; AAS 207th Meeting: Massive Binaries, 8-12 Jan. 2006, Washington, DC, USA Contract(s)/Grant(s): NSF 02-06150; Copyright; Avail.: Other Sources; Abstract Only
The very massive star, Eta Carinae, is enshrouded in an unusual complex environment of nebulosities and structures. The circumstellar gas gives rise to distinct absorption and emission components at different velocities and distances from the central source(s). Through photoionization modeling, we find that the radiation field from the more massive B-star companion supports the low ionization structure throughout the 5.54 year period. The radiation field of an evolved O-star is required to produce the higher ionization . emission seen across the broad maximum. Our studies utilize the HST/STIS data and model calculations of various regimes from doubly ionized species (T= 10,000K) to the low temperature (T = 760 K) conditions conductive to molecule formation (CH and OH). Overall analysis suggests the high depletion in C and O and the enrichment in He and N. The sharp molecular and ionic absorptions in this extensively CNO - processed material offers a unique environment for studying the chemistry, dust formation processes, and nucleosynthesis in the ejected layers of a highly evolved massive star. Author
Stellar Envelopes; O Stars; B Stars; Radiation Distribution; Photoionization; Massive Stars; Environmental Chemistry
20060012284 NASA Goddard Space Flight Center, Greenbelt, MD, USA
Searching for Radial Velocity Variations in eta Carinae
Iping, R. C.; Sonneborn, G.; Gull, T. R.; Ivarsson, S.; Nielsen, K.; Bullein of the American Astronomical Society; [2006]; Volume 37, No. 4; 1 pp.; In English; AAS 207th Meeting: Recent Discoveries in the Far UV, 8-12 Jan. 2006, Washington, DC, USA; Copyright; Avail.: Other Sources; Abstract Only
A hot companion of eta Carinae has been detected using high resolution spectra (905 - 1180 A) obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite (see poster by Sonneborn et al.). Analysis of the far-UV spectrum shows that eta Car B is a luminous hot star. The N II 1084-86 emission feature indicates that the star may be nitrogen rich. The FUV continuum and the S IV 1073 P-Cygni wind line suggest that the effective temperature of eta Car B is at least 25,000 K. FUV spectra of eta Carinae were obtained with the FUSE satellite at 9 epochs between 2000 February and 2005 July. The data consists of 12 observations taken with the LWRS aperture (30x30 arcsec), three with the HIRS aperture (1.25x20 arcsec), and one MRDS aperture (4x20 arcsec). In this paper we discuss the analysis of these spectra to search for radial velocity variations associated with the 5.54-year binary orbit of Eta Car AB. Author
Radial Velocity; Far UV Spectroscopic Explorer; Continuums; Hot Stars; Time Measurement; Explorer Satellites
20060012290 NASA Goddard Space Flight Center, Greenbelt, MD, USA
Dynamics of the Shocked Gas in the Eta Carinae System as Seen by Chandra
Corcoran, M. F.; Hamaguchi, K.; Henley, D. B.; Ishibashi, K.; Gull, T.; Nielsen, K.; Pittard, J. M.; Bulletin of the American Astronomical Society; [2006]; Volume 37, No. 4; 1 pp.; In English; AAS 207th Meeting, 8-12 Jan. 2006, Washington, DC, USA Contract(s)/Grant(s): GO3-4008A; Copyright; Avail.: Other Sources; Abstract Only
We report on a series of X-ray spectra of the supermassive star Eta Carinae obtained by the High Energy Transmission Grating Spectrometer on the CHANDRA X-ray observatory before, during and after the star's X-ray minimum in the summer of 2003. The X-ray spectra show significant variations in emission measure and absorption, in the strength of the iron K edge and fluorescent iron emission, but show little change in the distribution of emission measure with temperature. The CHANDRA spectra also resolve emission from Si, S, Fe and other elements in H-like and He-like configurations. The HETGS spectra show that these lines change in centroid energy along with evidence of changes in the forbidden-to-intercombination ratios of the He-like triplets. These spectra offer strong support that the X-ray emission originates within a shock cone around an unseen, massive companion. The variations of the X-ray line spectrum provide a direct measure of the dynamics of the shocked gas in this cone and also evidence that the hottest region of the shock is not always in collisional ionization equilibrium.We discuss these results in light of the recent discovery of He II 4686 emission and the reported discovery of FUV emission from the companion star. This work was supported by SAO/Chandra grant GO3-4008A. Author
Supermassive Stars; Companion Stars; X Ray Spectra; Energy Transfer; Gas Dynamics; Ionization; Centroids; Emission
20060012291 NASA Goddard Space Flight Center, Greenbelt, MD, USA
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Global X-ray Spectral Variation of Eta Carinae through the 2003 X-ray Minimum
Hamaguchi, K.; Corcoran, M. F.; White, N. E.; Gull, T.; Damineli, A.; Davidson, K.; Bulletin of the American Astronomical Society; January 2006; Volume 37, No. 4; 1 pp.; In English; AAS 207th Meeting: Massive Binaries, 8-12 Jan. 2006, Washington, DC, USA; Copyright; Avail.: Other Sources; Abstract Only
We report on the results of the X-ray observing campaign of the massive, evolved star Eta Carinae in 2003 around its recent X-ray Minimum, mainly using data from the XMM-Newton observatory. These imaging observations show that the hard X-ray source associated with the Eta Carinae system does not completely disappear in any of the observations during the Minimum. The variation of the spectral shape revealed two emission components. One newly discovered component did not exhibit any variation on kilo-second to year-long timescales, in a combined analysis with earlier ASCA and ROSAT data, and might represent the collision of a high speed outflow from Eta Carinae with ambient gas clouds. The other emission component was strongly variable in flux but the temperature of the hottest plasma did not vary significantly at any orbital phase. Absorption to the hard emission, was about a factor of three larger than the absorption determined from the cutoff of the soft emission, and reached a maximum of approx.4 x 10(exp 23)/sq cm before the Minimum. The thermal Fe\rm XXV emission line showed significant excesses on both the red and blue sides of the line outside the Minimum and exhibited a large redward excess during the Minimum. This variation in the line profile probably requires an abrupt change in ionization balance in the shocked gas. Author
X Ray Sources; Thermal Emission; Massive Stars; Plasma Temperature; Rosat Mission; Spectral Emission; Ionization
20060012302 NASA Goddard Space Flight Center, Greenbelt, MD, USA
X-ray Polarization Measurements with a Micro-pattern Gas Polarimeter
Hill, J. E.; Black, J. K.; Deines-Jones, P.; Jahoda, K.; Bellazzini, R.; Brez, A.; Costa, E.; Kaaret, P.; Minuti, M.; Spandre, G.; Swank, J. H.; January 2006; 1 pp.; In English; American Astronomical Society Conference, 8-12 Jan. 2006,Washington, DC, USA; Original contains black and white illustrations Contract(s)/Grant(s): NCC5-637; Copyright; Avail.: CASI: A01, Hardcopy
The benefits of Astrophysical X-ray polarization measurements have been discussed in the literature for decades and with respect to a variety of detectors. Despite this, a dedicated polarimeter for the measurement of Astrophysical sources has not flown since the 1970's, when the definitive measurement of the Crab Nebula was made. More recently, an indirect measurement of the polarization of two gamma-ray bursts has been extracted from BATSE data, re-emphasizing the importance of polarization measurements in constraining a physical model. We describe a sensitive and, and extremely versatile, photoelectric polarimeter using a micro-pattern gas detector, with an 80micron pixel ASIC anode, to image the primary photoelectron track. The detector can be optimized to a preferred energy range between 1 keV and 50 keV.We present measurements of polarized 4.5 keV X-rays and unpolarized 6 keV X-rays obtained with a prototype detector using Carbon Dioxide gas. Author
Gamma Ray Bursts; X Rays; Polarimeters; Photoelectrons; Gas Detectors; Gas Analysis; Gamma Ray Observatory; Pixels; Astrophysics
20060012304 NASA Goddard Space Flight Center, Greenbelt, MD, USA
Post-Launch Analysis of Swift's Gamma-Ray Burst Detection Sensitivity
Band, David L.; [2005]; 20 pp.; In English; Original contains black and white illustrations; No Copyright; Avail.: CASI: A03, Hardcopy
The dependence of Swift#s detection sensitivity on a burst#s temporal and spectral properties shapes the detected burst population. Using simplified models of the detector hardware and the burst trigger system I find that Swift is more sensitive to long, soft bursts than CGRO#s BATSE, a reference mission because of its large burst database. Thus Swift has increased sensitivity in the parameter space region into which time dilation and spectral redshifting shift high redshift bursts. Author
Gamma Ray Bursts; Red Shift; Relativistic Effects; Actuators
20060012312 NASA Goddard Space Flight Center, Greenbelt, MD, USA
Solving the Mystery of Short Gamma Ray Bursts
Gehrels, Neil; [2006]; 1 pp.; In English; No Copyright; Avail.: Other Sources; Abstract Only
Gamma-ray bursts are among the most fascinating occurrences in the cosmos. Until this year, the origin of short gamma-ray bursts was a complete mystery. A new NASA satellite named Swift has now captured the first images of these events and found that they are caused by tremendous explosions in the distant universe. Author
Explosions; Gamma Ray Bursts; Universe
20060012313 NASA Goddard Space Flight Center, Greenbelt, MD, USA
Observations of High-Energy Phenomena with Swift and GLAST
Gehrels, Neil; [2006]; 1 pp.; In English; No Copyright; Avail.: Other Sources; Abstract Only
The Swift and CLAST missions promise a great increase in our understanding of the gamma-ray universe. Swift was launched in November 2004 with a primary objective to study gamma-ray bursts. All instruments are performing well and more than 100 GRBs have been studied in detail. Major advances have already been made in the areas of short bursts, high redshift events and afterglow physics. The CLAST mission is scheduled for launch in fall 2007. It features a large new-technology instrument for high energy gamma-ray observations. Thousands of sources will be detected over a 5-10 year lifetime leading to the huge step forward in studies of the energetic gamma-ray sky. Author
Gamma Ray Bursts; Gamma Rays; Afterglows; Red Shift
20060012317 NASA Goddard Space Flight Center, Greenbelt, MD, USA
Rapid Centroids and the Refined Position Accuracy of the Swift Gamma-ray Burst Catalogue
Hill, J. E.; Angelini, L.; Moretti, A.; Morris, D. C.; Racusin, J.; Burrows, D. N.; Beardmore, A. P.; Campana, S.; Capalbi, M.; Kennea, J. A., et al.; [2005]; 5 pp.; In English; SWIFT Maryland Conference, 29 Nov. - 2 Dec. 2005, Washington, DC, USA; Original contains color and black and white illustrations Contract(s)/Grant(s): NAS5-00136; NCC5- 37; PPA/Z/S/2003/00507; I/R/039/04; Copyright; Avail.: CASI: A01, Hardcopy
The Swift X-ray Telescope autonomously refines the Burst Alert Telescope positions (approx.1-4' uncertainty) to better than 5 arcsec, within 5 seconds of target acquisition by the observatory for typical bursts. The results of the rapid positioning capability of the XRT are presented here for both known sources and newly discovered GRBs, demonstrating the ability to automatically utilize one of two integration times according to the burst brightness, and to correct the position for alignment offsets caused by the fast pointing performance and variable thermal environment of the satellite as measured by the Telescope Alignment Monitor. We present an evaluation of the position accuracy for both the onboard centroiding software and the ground software for the calibration targets and show that a significant improvement in position accuracy is obtained if the boresight detector position is optimized relative to the spacecraft pointing. Finally, we present an updated catalogue of Swift GRB X-ray positions obtained in Photon Counting Mode using the improved, calibrated boresight. Author
Centroids; Accuracy; Position Errors; Gamma Ray Bursts; X Ray Telescopes; Refining
20060012340 NASA Goddard Space Flight Center, Greenbelt, MD, USA
X-ray Polarimetry with a Micro-Pattern Gas Detector
Hill, Joe; [2005]; 26 pp.; In English; Original contains black and white illustrations Contract(s)/Grant(s): NCC5-637; No Copyright; Avail.: CASI: A03, Hardcopy
Topics covered include: Science drivers for X-ray polarimetry; Previous X-ray polarimetry designs; The photoelectric effect and imaging tracks; Micro-pattern gas polarimeter design concept. Further work includes: Verify results against simulator; Optimize pressure and characterize different gases for a given energy band; Optimize voltages for resolution and sensitivity; Test meshes with 80 micron pitch; Characterize ASIC operation; and Quantify quantum efficiency for optimum polarization sensitivity. Derived from text
X Rays; Polarimetry; Gas Detectors; Photoelectric Effect; Quantum Efficiency; Polarimeters; Energy Bands; Electric Potential; Optimization
20060012351 NASA Goddard Space Flight Center, Greenbelt, MD, USA
A Comprehensive Search for Gamma-Ray Lines in the First Year of Data from the INTEGRAL Spectrometer
Teegarden, B. J.; Watanabe, K.; [2006]; 40 pp.; In English; Original contains black and white illustrations; No Copyright; Avail.: CASI: A03, Hardcopy
Gamma-ray lines are produced in nature by a variety of different physical processes. They can be valuable astrophysical diagnostics providing information the may be unobtainable by other means. We have carried out an extensive search for gamma-ray lines in the first year of public data from the Spectrometer (SPI) on the INTEGRAL mission. INTEGRAL has spent a large fraction of its observing time in the Galactic Plane with particular concentration in the Galactic Center (GC) region (approximately 3 Msec in the first year). Hence the most sensitive search regions are in the Galactic Plane and Center. The phase space of the search spans the energy range 20-8000 keV, and line widths from 0-1000 keV (FWHM) and includes both diffuse and point-like emission. We have searched for variable emission on time scales down to approximately 1000 sec. Diffuse emission has been searched for on a range of different spatial scales from approximately 20 degrees (the approximate field-of-view of the spectrometer) up to the entire Galactic Plane. Our search procedures were verified by the recovery of the known gamma-ray lines at 511 keV and 1809 keV at the appropriate intensities and significances.We find no evidence for any previously unknown gamma-ray lines. The upper limits range from a few x10(exp -5) per square centimeter per second to a few x10(exp -3) per square centimeter per second depending on line width, energy and exposure. Comparison is made between our results and various prior predictions of astrophysical lines Author
Space Missions; Astrophysics; Gamma Ray Spectrometers; Line Spectra
20060013014 NASA Goddard Space Flight Center, Greenbelt, MD, USA
Simulating Gravitational Radiation from Binary Black Holes Mergers as LISA Sources
Baker, John; [2005]; 20 pp.; In English; Gravitational Wave Data Analysis Workshop, 4-17 Dec. 2005, Brownsville, TX, USA; Original contains black and white illustrations; No Copyright; Avail.: CASI: A03, Hardcopy
A viewgraph presentation on the simulation of gravitational waves from Binary Massive Black Holes with LISA observations is shown. The topics include: 1) Massive Black Holes (MBHs); 2) MBH Binaries; 3) Gravitational Wavws from MBH Binaries; 4) Observing with LISA; 5) How LISA sees MBH binary mergers; 6) MBH binary inspirals to LISA; 7) Numerical Relativity Simulations; 8) Numerical Relativity Challenges; 9) Recent Successes; 10) Goddard Team; 11) Binary Black Hole Simulations at Goddard; 12) Goddard Recent Advances; 13) Baker, et al.:GSFC; 13) Starting Farther Out; 14) Comparing Initial Separation; 15) Now with AMR; and 16) Conclusion.
CASI Black Holes (Astronomy); Gravitational Waves; Simulation; Binary Stars; LISA (Observatory)
20060013025 NASA Goddard Space Flight Center, Greenbelt, MD, USA
On Iron Enrichment, Star Formation, and Type Ia Supernovae in Galaxy Clusters
Loewenstein, Michael; [2006]; 54 pp.; In English; Original contains black and white illustrations Contract(s)/Grant(s): NNC5-640; No Copyright; Avail.: CASI: A04, Hardcopy
The nature of star formation and Type Ia supernovae (SNIa) in galaxies in the field and in rich galaxy clusters are contrasted by juxtaposing the buildup of heavy metals in the universe inferred from observed star formation and supernovae rate histories with data on the evolution of Fe abundances in the intracluster medium (ICM). Models for the chemical evolution of Fe in these environments are constructed, subject to observational constraints, for this purpose. While models with a mean delay for SNIa of 3 Gyr and standard initial mass function (IMF) are fully consistent with observations in the field, cluster Fe enrichment immediately tracked a rapid, top-heavy phase of star formation - although transport of Fe into the ICM may have been more prolonged and star formation likely continued beyond redshift 1. The means of this prompt enrichment consisted of SNII yielding greater than or equal to 0.1 solar mass per explosion (if the SNIa rate normalization is scaled down from its value in the field according to the relative number of candidate progenitor stars in the 3 - 8 solar mass range) and/or SNIa with short delay times originating during the rapid star formation epoch. Star formation is greater than 3 times more efficient in rich clusters than in the field, mitigating the overcooling problem in numerical cluster simulations. Both the fraction of baryons cycled through stars, and the fraction of the total present-day stellar mass in the form of stellar remnants, are substantially greater in clusters than in the field. Author
Galactic Clusters; Heavy Metals; Iron; Star Formation; Supernovae
20060013027 NASA Goddard Space Flight Center, Greenbelt, MD, USA
INTEGRAL Observations of the Galactic 511 keV Emission and MeV Gamma-ray Astrophysics
Watanabe, Ken; [2005]; 10 pp.; In English; Rironkon Symposium, 25-27 Dec. 2005, Kyoto, Japan; Original contains black and white illustrations; No Copyright; Avail.: CASI: A02, Hardcopy
Although there are a number of interesting phenomena, such as Nucleosynthesis in stars, in the MeV energy region, the observations have been difficult due to a small signal to noise (background) ratio (less than 1%). While NASA's Compton Gamma-ray Observatory (CGRO) enabled us to explore the Gamma-ray universe, ESA's INTEGRAL mission, launched in 2002, is providing us more detailed information with its superior energy and angular resolution. We will briefly discuss some of the current issues in MeV Gamma-ray Astrophysics. Then, we will focus on the Galactic 511 keV emission with the latest INTEGRAL observations, and talk about challenges we currently have. Author
Astrophysics; Gamma Ray Bursts; Space Missions; Universe
20060013116 NASA Goddard Space Flight Center, Greenbelt, MD, USA
Modeling the Self-organized Critical Behavior of the Plasma Sheet Reconnection Dynamics
Klimas, Alex; Uritsky, Vadim; Baker, Daniel; [2006]; 1 pp.; In English; International Living with the Stars Conference, 19-24 Feb. 2006, Goa, India; No Copyright; Avail.: Other Sources; Abstract Only
Analyses of Polar UVI auroral image data reviewed in our other presentation at this meeting (V. Uritsky, A. Klimas) show that bright night-side high-latitude UV emissions exhibit so many of the key properties of systems in self-organized criticality (SOC) that an alternate interpretation has become virtually impossible. It is now necessary to find and model the source of this behavior. We note that the most common models of self-organized criticality are numerical sandpiles. These are, at root, models that govern the transport of some quantity from a region where it is loaded to another where it is unloaded. Transport is enabled by the excitation of a local threshold instability; it is intermittent and bursty, and it exhibits a number of scale-free statistical properties. Searching for a system in the magnetosphere that is analogous and that, in addition, is known to produce auroral signatures, we focus on the reconnection dynamics of the plasma sheet. In our previous work, a driven reconnection model has been constructed and has been under study. The transport of electromagnetic (primarily magnetic) energy carried by the Poynting flux into the reconnection region of the model has been examined. All of the analysis techniques, and more, that have been applied to the auroral image data have also been applied to this Poynting flux. Here, we report new results showing that this model also exhibits so many of the key properties of systems in self-organized criticality that an alternate interpretation is implausible. Further, we find a strong correlation between these key properties of the model and those of the auroral UV emissions. We suggest that, in general, the driven reconnection model is an important step toward a realistic plasma physical model of self-organized criticality and we conclude, more specifically, that it is also a step in the right direction toward modeling the ultiscale reconnection dynamics of the magnetotail. Author
Magnetic Field Reconnection; Plasmas (Physics); Auroras; Plasma Layers; Polar Regions; Excitation
20060013134 NASA Goddard Space Flight Center, Greenbelt, MD, USA
Star Formation Rates in Cooling Flow Clusters: A UV Pilot Study with Archival XMM-Newton Optical Monitor Data
Hicks, A. K.; Mushotzky, R.; [2006]; 16 pp.; In English; Original contains black and white illustrations Contract(s)/Grant(s): NGT5-140 Report No.(s): astro-ph/0508143-v1; No Copyright; Avail.: CASI: A03, Hardcopy
We have analyzed XMM-Newton Optical Monitor (OM) UV (180-400 nm) data for a sample of 33 galaxies. 30 are cluster member galaxies, and nine of these are central cluster galaxies (CCGs) in cooling flow clusters having mass deposition rates which span a range of 8 - 525 Solar Mass/yr. By comparing the ratio of UV to 2MASS J band fluxes, we find a significant UV excess in many, but not all, cooling flow CCGs, a finding consistent with the outcome of previous studies based on optical imaging data (McNamara & O'Connell 1989; Cardiel, Gorgas, & Aragon-Salamanca 1998; Crawford et al. 1999). This UV excess is a direct indication of the presence of young massive stars, and therefore recent star formation, in these galaxies. Using the Starburst99 spectral energy distribution (SED) model of continuous star formation over a 900 Myr period, we derive star formation rates of 0.2 - 219 solar Mass/yr for the cooling flow sample. For 2/3 of this sample it is possible to equate Chandra/XMM cooling flow mass deposition rates with UV inferred star formation rates, for a combination of starburst lifetime and IMF slope. This is a pilot study of the well populated XMM UV cluster archive and a more extensive follow up study is currently underway. Author
Imaging Techniques; Galactic Clusters; Star Formation; Massive Stars; Spectral Energy Distribution; Flow Velocity; Starburst Galaxies
Source: NASA
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