Luminosity functions of gamma-ray burst afterglows

Free access article

Issue		A&A Volume 472, Number 2, September III 2007


Page(s)		L29 - L32
Section		Letters
DOI		http://dx.doi.org/10.1051/0004-6361:20078028

A&A 472, L29-L32 (2007)
DOI: 10.1051/0004-6361:20078028

Letter

Luminosity functions of gamma-ray burst afterglows

G. Jóhannesson, G. Björnsson, and E. H. Gudmundsson

Science Institute, University of Iceland, Dunhaga 3, 107 Reykjavik, Iceland
e-mail: gudlaugu@raunvis.hi.is

(Received 6 June 2007 / Accepted 12 July 2007 )

Abstract
Aims.Use the standard fireball model to create virtual populations of gamma-ray burst afterglows and study their luminosity functions.
Methods.We randomly vary the parameters of the standard fireball model to create virtual populations of afterglows. We use the luminosity of each burst at an observer's time of 1 day to create a luminosity function and compare our results with available observational data to assess the internal consistency of the standard fireball model.
Results.We show that the luminosity functions can be described by a function similar to a log normal distribution with an exponential cutoff. The function parameters are frequency dependent but not very dependent on the model parameter distributions used to create the virtual populations. Comparison with observations shows that while there is good general agreement with the data, it is difficult to explain simultaneously the X-ray and optical data. Possible reasons for this are discussed and the most likely one is that the standard fireball model is incomplete and that decoupling of the X-ray and optical emission mechanism may be needed.

Key words: gamma rays: bursts -- gamma rays: theory -- methods: numerical

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