We present the XMM-Newton observations of X-ray afterglows of the gamma-ray bursts GRB 011211 and GRB 001025. For GRB 011211, XMM detected a fading X-ray object with an average flux in 0.2-10 keV declining from 2.7×10-13 ergs s-1 cm-2 during the first 5 ks of the 27 ks observation to 1.0×10-13 ergs s-1 cm-2 toward the end of the observation. The spectrum of the afterglow can be fitted to a power law with α=2.16+/-0.03 modified for the Galactic absorption. No significant evolution of spectral parameters has been detected during the observation. A similar X-ray spectrum with α=2.01+/-0.09 has been observed by the XMM from GRB 001025. The nondetection of any extra absorption in these spectra above the Galactic value is an interesting fact and may impose restrictions on the favorable GRB models involving the burst origin in star-forming regions. Finally, we discuss soft X-ray lines from GRB 011211 reported by Reeves et al. and conclude that there is no definitive evidence for the presence of these lines in the spectrum.
The Astrophysical Journal
- Pub Date:
- February 2003
- Gamma Rays: Bursts;
- X-Rays: Individual: Alphanumeric: GRB 001025;
- X-Rays: Individual: Alphanumeric: GRB 011211;
- submitted to ApJL (7 pages, 4 figures, 2 tables, emulateapj.sty)