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28 March 2024
 
  » arxiv » astro-ph/0401580

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Formation Rate, Evolving Luminosity Function, Jet Structure, and Progenitors for Long Gamma-Ray Bursts
C. Firmani ; V. Avila-Reese ; G. Ghisellini ; A.V. Tutukov ;
Date 28 Dec 2003
Journal Astrophys.J. 611 (2004) 1033-1040
Subject astro-ph
Affiliation1,2), V. Avila-Reese , G. Ghisellini , A.V. Tutukov (OAB, Italy IA-UNAM, Mexico INASAN, Russia
AbstractWe constrain the isotropic luminosity function (LF) and formation rate of long gamma-ray bursts (GRBs) by fitting models ’jointly’ to both the observed differential peak flux and redshift distributions. We find evidence supporting an evolving LF, where the luminosity scales as (1+z)^delta with an optimal delta of 1.0pm 0.2. For a single power-law LF, the best slope is ~ -1.57 with an upper luminosity of 10^53.3 erg/s, while the best slopes for a double power-law LF are approximately -1.6 and -2.6 with a break luminosity of 10^52.7 erg/s. Our finding implies a jet model intermediate between the universal structured epsilon(theta) proportional to theta^-2 model and the quasi-universal Gaussian structured model. For the uniform jet model our result is compatible with an angle distribution between 2 and 15 grades. Our best constrained GRB formation rate histories increase from z=0 to z=2 by a factor of ~30 and then continue increasing slightly. We connect these histories to that of the cosmic star formation history, and compare with observational inferences up to z~6. GRBs could be tracing the cosmic rates of both the normal and obscured star formation regimes. We estimate a current GRB event rate in the Milky Way of ~5 10^-5 yr^-1, and compare it with the birthrate of massive close WR+BH binaries with orbital periods of hours. The agreement is rather good suggesting that these systems could be the progenitors of the long GRBs.
Source arXiv, astro-ph/0401580
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