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|Title:||The soft X-ray blast in the apparently sub-luminous GRB 031203|
Vaughan, S. A.
Fynbo, J. P. U.
O'Brien, P. T.
Osborne, J. P.
Reeves, J. N.
Tedds, Jonathan A.
Watson, M. G.
|Publisher:||IOP Publishing for American Astronomical Society|
|Citation:||Astrophysical Journal, 636, pp. 967-970|
|Abstract:||GRB031203 was a very low apparent luminosity gamma-ray burst (GRB). It was also the first GRB with a dust-scattered X-ray halo. The observation of the halo allowed us to infer the presence of a large soft X-ray fluence in the total burst output. It has, however, also been claimed that GRB031203 was intrinsically sub-energetic, representative of a class of spectrally hard, low-energy bursts quite different from other GRBs. Reanalysis of the available data confirms our original finding that GRB031203 had a very large soft X-ray component, the time of which can be constrained to within a few minutes after the burst, implying that while GRB031203 did indeed have a very low apparent luminosity, it was also very soft. Notions propagated in the literature regarding the uncertainties in the determination of the soft X-ray fluence from the halo data and on the available constraints from the hard X-ray data are addressed: the properties of the scattering dust along the line of sight (grain sizes, precise location and the geometry) are determined directly from the high quality X-ray data so that there is little uncertainty about the scatterer; constraints on the X-ray lightcurve from the Integral spacecraft at the time of the soft X-ray blast are not complete because of a slew in the spacecraft pointing shortly after the burst. Claims that GRB031203 was intrinsically under-energetic and that it represents a deviation from the luminosity-peak energy relation do not appear to be substantiated by the data, regardless of whether the soft X-ray component is declared part of the prompt emission or the afterglow. We conclude that the difference between the soft and hard X-ray spectra from XMM-Newton and Integral indicate that a second soft pulse probably occurred in this burst as has been observed in other GRBs, notably GRB050502B.|
|Rights:||Copyright © 2006, The American Astronomical Society. Deposited with reference to the publisher’s open access archiving policy|
|Description:||4 pages, 2 figures, emulateapj Accepted for publication in ApJ, scheduled 10 January 2006 issue|
|Appears in Collections:||Published Articles, Dept. of Physics and Astronomy|
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