Cumulative light curves of gamma-ray bursts and relaxation systems

Free access article

Issue		A&A Volume 393, Number 2, October II 2002


Page(s)		L29 - L32
Section		Letters
DOI		http://dx.doi.org/10.1051/0004-6361:20021073

A&A 393, L29-L32 (2002)
DOI: 10.1051/0004-6361:20021073

Letter

Cumulative light curves of gamma-ray bursts and relaxation systems

S. McBreen¹, B. McBreen¹, L. Hanlon¹ and F. Quilligan^{1, 2}

¹ Department of Experimental Physics, University College Dublin, Dublin 4, Ireland
² Intel Corporation, Leixlip, Co. Kildare, Ireland

(Received 24 May 2002 / Accepted 22 July 2002 )

Abstract
The cumulative light curves of a large sample of gamma ray bursts (GRBs) were obtained by summing the BATSE counts. The smoothed profiles are much simpler than the complex and erratic running light curves that are normally used. For most GRBs the slope of the cumulative light curve ( S) is approximately constant over a large fraction of the burst. The bursts are modelled as relaxation systems that continuously accumulate energy in the reservoir and discontinuously release it. The slope is a measure of the cumulative power output of the central engine. A plot of S versus peak flux in 64 ms ( $P_{64\, {\rm ms}}$ ) shows a very good correlation over a wide range for both long and short GRBs. No relationship was found between S and the GRBs with known redshift. The standard slope ( $S^{\prime}$ ), which is representative of the power output per unit time, is correlated separately with $P_{64\, {\rm ms}}$ for both sub-classes indicating more powerful outbursts for the short GRBs. $S^{\prime}$ is also anticorrelated with GRB duration. These results imply that GRBs are powered by accretion into a black hole.

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

Offprint request: S. McBreen, smcbreen@bermuda.ucd.ie

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