Bulletin of the American Physical Society
2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009; Denver, Colorado
Session W8: Gamma Ray Bursts |
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Sponsoring Units: DAP Chair: Enrico Ramirez-Ruiz, University of California, Santa Cruz Room: Governor's Square 17 |
Tuesday, May 5, 2009 10:45AM - 10:57AM |
W8.00001: Simulations of Supernova Shock Breakout Lucille Frey, Chris Fryer, Aimee Hungerford As the radiation-dominated shock wave from core collapse approaches the stellar surface, or the edge of a dense stellar wind, the optical depth of the plasma ahead of the shock decreases until radiation escapes in a burst. This shock breakout (SBO) burst occurs days or weeks before the optical light from radioactive decay peaks and can be used to determine the radius of the progenitor star or its recent mass loss history. Several recently observed X-ray and UV bursts associated with supernovae have been interpreted as shock breakout (SBO) observations, though this interpretation is still being debated. We use a radiation-hydrodynamics code with adaptive mesh refinement to follow the motion of the radiation-dominated shock through SBO with high resolution. We run a suite of one dimensional simulations using binary and single progenitors with a range of explosion energies, wind velocities and mass loss histories, allowing us to compare shock interactions with the stellar atmosphere, wind and previously ejected shells. These simulations will better constrain the properties of the progenitor star and its environment that can be derived from SBO observations. [Preview Abstract] |
Tuesday, May 5, 2009 10:57AM - 11:09AM |
W8.00002: The Formation of Black Holes in Failing Core-Collapse Supernovae Evan O'Connor, Christian D. Ott, E. Sterl Phinney We present new simulations of black hole formation in dying massive stars using 1D GR hydrodynamics, multiple finite-temperature nuclear equations of state and parameterized neutrino heating and cooling. Via a sweep through the progenitor mass range from 10 to 100 solar masses, metallicity from zero to solar and various neutrino luminosities/heating efficiencies, we establish for the first time in a systematic fashion the conditions necessary for black hole formation to occur in the limiting case of spherically-symmetric postbounce core-collapse dynamics. Since multi-D effects such as rotation or convective overturn can act only to prolong the time to black hole formation or prevent it altogether, our new results also constrain collapsar/GRB progenitor stellar structure. [Preview Abstract] |
Tuesday, May 5, 2009 11:09AM - 11:21AM |
W8.00003: Modeling and Interpretation of High Energy Emission from GRBs Observed with the Fermi Gamma Ray Space Telescope Soebur Razzaque Fermi Large Area Telescope (LAT) has detected high-energy emission ($>$100 MeV) from several Gamma Ray Bursts. LAT data show a delay in arrival time of $>$100 MeV emission as compared to keV--MeV emission detected by Fermi Gamma Ray Burst Monitor (GBM), a feature common to all these GRBs. The most detailed data yet of the high-energy emission came from the extremely fluent GRB 080916C. An analysis of the data for GRB 080916C with measured redshift is used to constrain the total energy, the bulk Lorentz factor of the jet, and the emission region size scale. Different possible mechanisms are examined in order to explain the delayed onset of the high-energy emission. The most stringent limit to date on the quantum gravity mass scale, derived from the GRB 080916C data, is also presented. [Preview Abstract] |
Tuesday, May 5, 2009 11:21AM - 11:33AM |
W8.00004: ABSTRACT WITHDRAWN |
Tuesday, May 5, 2009 11:33AM - 11:45AM |
W8.00005: ABSTRACT WITHDRAWN |
Tuesday, May 5, 2009 11:45AM - 11:57AM |
W8.00006: The classification of GRB050509B within the canonical GRB scenario Gustavo De Barros, Maria Grazia Bernardini, Carlo Luciano Bianco, Letizia Caito, Remo Ruffini Within the fireshell model, the canonical GRB scenario emphasizes the existence of two sharply different components: 1) the proper GRB (P-GRB), emitted at the transparency of the fireshell; 2) the ``extended afterglow'', due to the interaction of the optically thin fireshell with the CircumBurst Medium (CBM). Modifying the relative intensities of these components all GRBs can be classified into the traditionally called ``long'' GRBs, the ``fake'' or ``disguised'' short GRBs and the ``genuine'' short GRBs. We show as a specific example for this classification the case of GRB050509B, considered in the literature as ``short GRB with associated afterglow''. We analysed this GRB and we show that its astrophysical setting suggests univocally a classification as ``fake'' short GRB. Moreover, we show how the Amati relation is crucial in identifying the nature of GRBs, expecially in cases of pucity of observational data. [Preview Abstract] |
Tuesday, May 5, 2009 11:57AM - 12:09PM |
W8.00007: ABSTRACT WITHDRAWN |
Tuesday, May 5, 2009 12:09PM - 12:21PM |
W8.00008: Long, short and fake short GRBs in the canonical GRB scenario Remo Ruffini, Maria Grazia Bernardini, Carlo Luciano Bianco, Letizia Caito, Gustavo De Barros We will show how all GRBs can be classified into a) the traditionally called ``long'' GRBs, b) the ``fake'' or ``disguised'' short GRBs and c) the ``genuine'' short GRBs. Samples of such classifications will be given, as well as considerations on their astrophysical progenitors. This is grounded on the canonical GRB structure implied by the fireshell model, which emphasized the existence of two sharply different components: 1) the proper GRB (P-GRB), emitted at the fireshell transparency; 2) the ``extended afterglow'', due to the interaction of the leftover accelerated baryons and leptons with the CircumBurst Medium (CBM). The total energy and baryon loading of the fireshell determines the relative energetics and the temporal separation between the peaks of such two components. After the observations by Swift, it has become clear that the extended afterglow emission is itself divided into two distinct components: the prompt emission phase, and a plateau phase followed by a decaying phase. The prompt emission represents the interaction of the ultrarelativistic baryons with the CBM inhomogeneities, described by a thermal radiation in the comoving frame. [Preview Abstract] |
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