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Issue A&A Volume 393, Number 1, October I 2002 Page(s) L15 - L19 Section Letters DOI 10.1051/0004-6361:20021170

A&A 393, L15-L19 (2002)
DOI: 10.1051/0004-6361:20021170

Letter

Kerr black holes and time profiles of gamma ray bursts

S. McBreen¹, B. McBreen¹, L. Hanlon¹ and F. Quilligan<sup>1, 2

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

(Received 11 June 2002 / Accepted 9 August 2002)

Abstract
The cumulative light curves of Gamma Ray Bursts (GRBs) smooth the spiky nature of the running light curve. The cumulative count increases in an approximate linear way with time  t for most bursts. In 19 out of 398 GRBs with T₉₀ > 2  s, the cumulative light curve was found to increase with time as ~ t² implying a linear increase in the running light curve. The non-linear sections last for a substantial fraction of the GRB duration, have a large proportion of the cumulative count and many resolved pulses that usually end with the highest pulse in the burst. The reverse behaviour was found in 11 GRBs where the running light curve decreased with time and some bursts are good mirror images of the increases. These GRBs are among the spectrally hardest bursts observed by BATSE. The most likely interpretation is that these effects are signatures of black holes that are either being spun up or down in the accretion process. In the spin up case, the increasing Kerr parameter of the black hole allows additional rotational and accretion energy to become available for extraction. The process is reversed if the black hole is spun down by magnetic field torques. The luminosity changes in GRBs are consistent with the predictions of the BZ process and neutrino annihilation and thus provide the link to spinning black holes. GRBs provide a new window for studying the general relativistic effects of Kerr black holes.

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

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

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