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Gamma-Ray Bursts: the Isotropic-Equivalent-Energy Function and the Cosmic Formation Rate
- Publication Year :
- 2011
- Publisher :
- arXiv, 2011.
-
Abstract
- Gamma-ray bursts (GRBs) are brief but intense emission of soft $\gamma-$rays, mostly lasting from a few seconds to a few thousand seconds. For such kind of high energy transients, their isotropic-equivalent-energy ($E_{\rm iso}$) function may be more scientifically meaningful when compared with GRB isotropic-equivalent-luminosity function ($L_{\rm iso}$), as the traditional luminosity function refers to steady emission much longer than a few thousand seconds. In this work we for the first time construct the isotropic-equivalent-energy function for a sample of 95 bursts with measured redshifts ($z$) and find an excess of high-$z$ GRBs. Assuming that the excess is caused by a GRB luminosity function evolution in a power-law form, we find a cosmic evolution of $E_{\rm iso}\propto(1+z)^{1.80^{+0.36}_{-0.63}}$, which is comparable to that between $L_{\rm iso}$ and $z$, i.e., $L_{\rm iso}\propto(1+z)^{2.30^{+0.56}_{-0.51}}$ (both $1\sigma$). The evolution-removed isotropic-equivalent-energy function can be reasonably fitted by a broken power-law, in which the dim and bright segments are $\psi(E_{\rm iso})\propto E_{\rm iso}^{-0.27\pm0.01}$ and $\psi(E_{\rm iso})\propto E_{\rm iso}^{-0.87\pm0.07}$, respectively ($1\sigma$). For the cosmic GRB formation rate, it increases quickly in the region of $0 \leq z \lesssim 1$, and roughly keeps constant for $1\lesssim z \lesssim 4$, and finally falls with a power index of $-3.80\pm2.16$ for $z\gtrsim 4$, in good agreement with the observed cosmic star formation rate so far.<br />Comment: 6 pages, 10 figures. Accepted for publication in MNRAS
- Subjects :
- High Energy Astrophysical Phenomena (astro-ph.HE)
Astrophysics::High Energy Astrophysical Phenomena
FOS: Physical sciences
High Energy Physics::Experiment
Astrophysics::Cosmology and Extragalactic Astrophysics
Astrophysics - High Energy Astrophysical Phenomena
Astrophysics::Galaxy Astrophysics
Subjects
Details
- Database :
- OpenAIRE
- Accession number :
- edsair.doi.dedup.....d0aecf1c2f7d4f4f28d5a516e934e280
- Full Text :
- https://doi.org/10.48550/arxiv.1112.2029