INTEGRAL and XMM-Newton Observations of the Weak Gamma-Ray Burst GRB 030227

Abstract

We present International Gamma-Ray Astrophysical Laboratory (INTEGRAL) and XMM-Newton observations of the prompt γ-ray emission and the X-ray afterglow of GRB 030227, the first gamma-ray burst for which the quick localization obtained with the INTEGRAL Burst Alert System has led to the discovery of X-ray and optical afterglows. GRB 030227 had a duration of about 20 s and a peak flux of ~1.1 photons cm-2 s-1 in the 20-200 keV energy range. The time-averaged spectrum can be fitted by a single power law with photon index ~2, and we find some evidence for a hard-to-soft spectral evolution. The X-ray afterglow has been detected starting only 8 hr after the prompt emission, with a 0.2-10 keV flux decreasing as t-1 from 1.3 × 10-12 to 5 × 10-13 ergs cm-2 s-1. The afterglow spectrum is well described by a power law with photon index 1.94 ± 0.05 modified by a redshifted neutral absorber with column density of several 1022 cm-2. A possible emission line at 1.67 keV could be due to Fe for a redshift z ~ 3, consistent with the value inferred from the absorption.