AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 3. Gamma Ray Bursts
Display, Monday, May 31, 1999, 9:20am-6:30pm, Southwest Exhibit Hall

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[3.02] A Monte Carlo Universe of Gamma-Ray Bursts

G.F. Marani (NASA/NRC), R.J. Nemiroff (Michigan Tech), J.T. Bonnell (NASA/USRA), J.P. Norris (NASA/GSFC)

Can any spatial distribution of gamma-ray bursts (GRBs) fit the measured optical transient redshifts, Log N =96 Log P, duration distribution, and hardness distribution? In an effort to answer this question, we have created a Monte Carlo code that simulates a universe filled with GRBs. We model potential GRB luminosity distributions, cosmologies, density evolution, spectral diversity, and the duration distribution. We find that large time-dilation factors (~> 2.5) are difficult to mimic for a wide range of luminosity distributions, and for different cosmic star formation scenarios. However, trigger selection effects, which include in the sample essentially all bright bursts -- regardless of pulse and duration timescales -- but exclude bursts with shorter temporal structures, were not accounted for in previous time-dilation measurements. We will present results which attempt to correct for this additional selection effect and compare with current modeling. Attributes of the code and further implications will be discussed.

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