EDP Sciences
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Volume 401, Number 1, April I 2003
Page(s) 129 - 140
Section Galactic structure and dynamics
DOI http://dx.doi.org/10.1051/0004-6361:20021863

A&A 401, 129-140 (2003)
DOI: 10.1051/0004-6361:20021863

On the difference between the short and long gamma-ray bursts

L. G. Balázs1, Z. Bagoly2, I. Horváth3, A. Mészáros4 and P. Mészáros5

1  Konkoly Observatory, Budapest, Box 67, 1525, Hungary
2  Laboratory for Information Technology, Eötvös University, Budapest, Pázmány Péter sétány 1/A, 1117, Hungary
    e-mail: bagoly@ludens.elte.hu
3  Dept. of Physics, Bolyai Military University, Budapest, Box 12, 1456, Hungary
    e-mail: hoi@bjkmf.hu
4  Astronomical Institute of the Charles University, 180 00 Prague 8, V Holesovickách 2, Czech Republic
    e-mail: meszaros@mbox.cesnet.cz
5  Dept. of Astronomy & Astrophysics, Pennsylvania State University, 525 Davey Lab
    e-mail: nnp@astro.psu.edu

(Received 29 August 2002 / Accepted 16 December 2002)

We argue that the distributions of both the intrinsic fluence and the intrinsic duration of the $\gamma$-ray emission in gamma-ray bursts from the BATSE sample are well represented by log-normal distributions, in which the intrinsic dispersion is much larger than the cosmological time dilatation and redshift effects. We perform separate bivariate log-normal distribution fits to the BATSE short and long burst samples. The bivariate log-normal behaviour results in an ellipsoidal distribution, whose major axis determines an overall statistical relation between the fluence and the duration. We show that this fit provides evidence for a power-law dependence between the fluence and the duration, with a statistically significant different index for the long and short groups. We discuss possible biases, which might affect this result, and argue that the effect is probably real. This may provide a potentially useful constraint for models of long and short bursts.

Key words: gamma-rays: bursts -- methods: statistical -- methods: data analysis

Offprint request: L. G. Balázs, balazs@konkoly.hu

© ESO 2003