8th HEAD Meeting, 8-11 September, 2004
Session 22 Gamma-ray Bursts
Oral, Friday, September 10, 2004, 9:00-10:30am

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[22.02] GRB 031203: A low luminosity X-ray flash with a Galactic halo

J. P. Osborne, S. Vaughan (University of Leicester), D. Watson, J. Hjorth (University of Copenhagen), P. T. O'Brien, R. Willingale (University of Leicester), J. N. Reeves (USRA/GSFC)

XMM-Newton observations of GRB 031203 revealed apparently expanding X-ray rings centered on the afterglow. These beautiful and unique concentric halos were due to scattering by dust in our Galaxy of soft X-ray emission within an hour of the burst. It is natural to associate this emission with the GRB, leading us to identify this as a very soft X-ray flash. The low redshift of 0.105 leads to a very low isotropic energy, intermediate between that of GRB 980425 and the values of more typical GRBs. The Amati and Atteia relationships result in a redshift and Epeak consistent with the observed values, demonstrating that this GRB/XRF, although unusually soft, close and low luminosity, follows some normal GRB patterns. However, the low luminosity and unusual fast-then-slow X-ray decay behaviour hint at large jet opening and viewing angles.

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Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.