EDP Sciences
Free access
Volume 418, Number 2, May I 2004
Page(s) 487 - 493
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20034567

A&A 418, 487-493 (2004)
DOI: 10.1051/0004-6361:20034567

Bimodal distribution of the autocorrelation function in gamma-ray bursts

L. Borgonovo

Stockholm Observatory, 10691 Stockholm, Sweden
(Received 23 October 2003 / Accepted 2 February 2004 )

Autocorrelation functions (ACFs) are studied for a sample of 16 long gamma-ray bursts (GRBs) with known redshift  z, that were observed by the BATSE and Konus experiments. When corrected for cosmic time dilation, the ACF shows a bimodal distribution. A narrow width class (11 bursts) has at half-maximum a mean width $\tau'_0=1.6$ s with a relative dispersion of $\sim $32%, while a broad width class (5 bursts) has $\tau'_0=7.5$ s with a $\sim $4% dispersion. The separation between the two mean values is highly significant ( ${>}7\sigma$). This temporal property could be used on the large existing database of GRBs with unknown redshift. The broad width set shows a very good linear correlation between width at half-maximum and (1+z), with a correlation coefficient R=0.995 and a probability of chance alignment <0.0004. The potential application of this correlation to cosmology studies is discussed, using it in combination with recently proposed luminosity indicators.

Key words: gamma rays: bursts -- gamma rays: observations -- methods: data analysis -- cosmology: distance scale

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