Bulletin of the American Physical Society
2005 APS April Meeting
Saturday–Tuesday, April 16–19, 2005; Tampa, FL
Session H9: Hard X Rays and Gamma Rays |
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Sponsoring Units: DAP Chair: Fiona Harrison, Caltech Room: Marriott Tampa Waterside Room 5 |
Sunday, April 17, 2005 8:30AM - 8:42AM |
H9.00001: SPI/INTEGRAL measurement of the Central radian soft gamma-ray continuum emission Bouchet Laurent, Roques Jean-Pierre It is clear now that unresolved sources contribute for the greatest part to the soft gamma-ray ``diffuse emission'' estimated by past instruments, and that always better sensitivity of the instruments leads to continuous reduction of this ``diffuse emission.'' The last stage is brought now by the INTEGRAL observatory. INTEGRAL is performing a deep survey of the central radian of the galaxy. First, we have built a catalogue of the hard sources of X-ray ($>$ 20 keV) detected by SPI/INTEGRAL, extracted their spectra and light curves simultaneously as the ``diffuse emission'' flux whose morphology has been represented with a simple analytical model. Finally we compared the total sources and the ``diffuse emission'' contributions. [Preview Abstract] |
Sunday, April 17, 2005 8:42AM - 8:54AM |
H9.00002: INTEGRAL/SPI Observations of the Inner-Galaxy Region Roland Diehl, Jean-Pierre Roques The INTEGRAL mission has conducted a survey of the inner Galaxy region as part of its core program. Interesting results have been obtained for diffuse emissions in the continuum from X-rays to MeV energies, and from lines attributed to positron annihilation, and to radioactive isotopes $^{26}$Al and $^{60}$Fe. Additionally, compact sources (steady and variable) have been surveyed. This paper will review results after two mission years in the areas of interstellar diffuse emission and its origin, the number of compact high-energy sources in this region, positron annihilation conditions, and sources of fresh nucleosynthesis products. [Preview Abstract] |
Sunday, April 17, 2005 8:54AM - 9:06AM |
H9.00003: Recent Results from the InFOC$\mu$S Hard X-Ray Imaging Telescope Jack Tueller InFOC$\mu$S is a new generation balloon-borne hard X-ray telescope with focusing optics and spectroscopy. We had a successful 22.5 hour flight from Fort Sumner, NM on September 16-17, 2004. In this paper, we present the performance of the hard X-ray telescope and recent scientific results. InFOC$\mu$S detected three galactic sources, 4U 0115+63, Cygnus X-1 and Hercules X-1. Spectral measurements in the 20-50 keV energy range will be presented for these sources. The telescope consists of a depth-graded platinum-carbon multilayer mirror with an 8 m focal length and a CdZnTe detector. Supermirrors are coated on thin aluminum substrates (150\mum) as reflectors. It has an effective area of 49 cm$^2$ at 30 keV, an angular resolution of 2.6 arcmin (HPD), and a field of view of 10 arcmin. The CdZnTe detector is a pixellated solid-state device capable of imaging spectroscopy. The detector is surrounded by a 3-cm thick CsI anti coincidence shield to reduce background from particles and photons not incident along the mirror focal direction. Detailed performance based on ground calibration results are presented. [Preview Abstract] |
Sunday, April 17, 2005 9:06AM - 9:18AM |
H9.00004: Current Developments towards a Xenon Advanced Compton Telescope Uwe Oberlack, Elena Aprile, Karl-Ludwig Giboni, Daniel Kocevski Gamma-ray astronomy in the energy range of nuclear transitions holds great promise for a great number of astrophysical questions. Gamma-ray lines, in particular, probe deeply into the explosion mechanisms of supernovae and provide unique insight into formation, evolution, and death of stars and their associated nucleosynthesis. Yet, the most exciting science topics have barely been probed by gamma-ray telescopes to-date. Sensitivity is therefore the most important characteristic of a next-generation instrument. An ``Advanced Compton Telescope,'' a visionary NASA mission currently under study, aims at improving sensitivity 100-fold over current instruments. We have recently been approved to continue the development of a detector technology based on multiple liquid xenon time projection chambers (LXeTPC). Recent advances in UV photosensors have opened new opportunities for the successful development of a Xenon ACT. These are: (a) Improvement of Energy Resolution by combination of charge and scintillation. (b) Application of Time-of-Flight in a compact telescope configuration. We report on the status of the LXeTPC technology to-date, and on our current and planned efforts to develop a telescope module that will meet the ACT challenge. [Preview Abstract] |
Sunday, April 17, 2005 9:18AM - 9:30AM |
H9.00005: The Galactic Positron Annihilation Medium: Is Ionized Helium A Viable Candidate? Matthew Franking, Benjamin Brown, Jennifer Chapin We consider the possibility that the 511 keV electron-positron annihilation line coming from the direction of the galactic center could be the result of thermal positrons annihilating via Ps formation from charge exchange with singly ionized helium.[Fatuzzo:2000] We present an analysis of the galactic line profiles, comparing the observed line shape to the expected line shape for the proposed annihilation mechanism at various temperatures. We calculate the FWHM by both Monte Carlo and analytical techniques, using empirically derived Ps formation, ionization, and excitation cross sections for the e$^{+}$- He$^{+}$ interactions. It is found that the FWHM of the annihilation spectrum for this process shows a logarithmic temperature dependence. We conclude that ionized helium is an unlikely annihilation medium for a reasonable ambient electron temperature, given that the calculated FWHM exceeds the upper maximum of the error bars of the weighted average of the line widths of all observations known to the authors. \newline \newline [Fatuzzo:2000] M. Fatuzzo, F. Melia, and J. Rafelski, Astrophys. J. 549, 293 (2000) [Preview Abstract] |
Sunday, April 17, 2005 9:30AM - 9:42AM |
H9.00006: The Gamma-ray Large Area Space Telescope (GLAST) Steven Ritz The Gamma-ray Large Area Space Telescope, GLAST, is a mission under construction to measure the cosmic gamma-ray flux in the energy range 20 MeV to $>$300 GeV, with supporting measurements for gamma-ray bursts from 10 keV to 25 MeV. With its launch in 2007, GLAST will open a new and important window on a wide variety of high energy phenomena, including black holes and active galactic nuclei; gamma-ray bursts; the origin of cosmic rays and supernova remnants; and searches for hypothetical new phenomena such as supersymmetric dark matter annihilations, Lorentz invariance violation, and exotic relics from the Big Bang. In addition to the science opportunities, this talk will include a brief description of the instruments, the opportunities for guest observers, and the mission status. [Preview Abstract] |
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