Observations of the X-ray Afterglows of GRB011211 and GRB001025 by XMM-Newton

Abstract

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 fading X-ray object with an average flux in 0.2-10 keV declining from 2.7$\times 10^{-13}$ erg cm${}^{-2}$ s${}^{-1}$ during the first 5 ks of 27-ks observation to 1.0$\times 10^{-13}$ erg cm${}^{-2}$ s${}^{-1}$ toward the end of the observation. The spectrum of the afterglow can be fit to a power law with alpha=2.16$\pm$0.03 modified for the Galactic absorption. No significant evolution of spectral parameters has been detected during the observation. Similar X-ray spectrum with alpha=2.01$\pm$0.09 has been observed by the XMM from the GRB 001025. The non-detection of any extra absorption in these spectra above the Galactic value is an interesting fact and may impose restrictions to the favorable GRB models involving burst origin in star-forming regions. Finally we discuss soft X-ray lines from GRB 011211 reported by Reeves et al.(2002) and conclude that there is no definitive evidence for the presense of these lines in the spectrum.

submitted to ApJL (7 pages, 4 figures, 2 tables, emulateapj.sty)

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• Models for Achromatic Light-Curve Breaks in GRB Afterglows: Jets, Structured Outflows, and Energy Injection
• Statistical Re-examination of Reported Emission Lines in the X-ray Afterglow of GRB 011211
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• Observational Implications of a Plerionic Environment for GRBs
• INTEGRAL and XMM-Newton observations of the weak GRB 030227
• Non-detection of the Gamma-ray Burst X-ray Emission Line: The Down-Comptonization Effect
• Reconsidering the origin of the X-ray emission lines in GRB 011211
• GRB011211: An alternative interpretation of the optical and X-ray spectra in terms of blueshifts