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Issue A&A
Volume 376, Number 1, September II 2001
Page(s) 10 - 16
Section Cosmology
DOI http://dx.doi.org/10.1051/0004-6361:20010932



A&A 376, 10-16 (2001)
DOI: 10.1051/0004-6361:20010932

Luminosity function of GRBs

S. Sethi1 and S. G. Bhargavi2

1  Harish-chandra Research Institute, Jhusi Road, Allahabad 211 019, India
    e-mail: sethi@mri.ernet.in
2  Indian Institute of Astrophysics, Sarjapur Road, Bangalore 560 034, India
    e-mail: bhargavi@iiap.ernet.in

(Received 12 February 2001 / Accepted 29 June 2001 )

Abstract
We attempt to constrain the luminosity function of Gamma Ray Bursts (GRBs) from the observed number count-flux relation and the afterglow redshift data. We assume three classes of luminosity functions for our analysis: (a) Log-normal distribution, (b) Schechter distribution, and (c) Scale-free distribution. We assume several models of the evolution of the GRB population for each luminosity function. Our analysis shows that: (a) log-normal is the only luminosity function that is compatible with both the observations. This result is independent of the GRB evolution model, (b) for log-normal function, the average photon luminosity L0 and the width of the luminosity function $\sigma$ that are compatible with both the observations fall in the range: $10^{55} {\rm s^{-1}} \la L_0 \la 10^{56} {\rm s^{-1}}$ and $ 2 \la \sigma \la 3$, (c) the agreement of observations with other luminosity functions requires the GRB population to evolve more strongly than the evolution of the star-formation rate of the universe.


Key words: gamma rays: bursts -- cosmology: observations

Offprint request: S. Sethi, sethi@mri.ernet.in

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© ESO 2001


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