SWIFT and XMM-Newton observations of the extraordinary gamma-ray burst 060729: More than 125 days of X-ray afterglow

Dirk Grupe, Caryl Gronwall, Xiang Yu Wang, Peter W.A. Roming, Jay Cummings, Bing Zhang, Peter Mészáros, Maria Diaz Trigo, Paul T. O'Brien, Kim L. Page, Andy Beardmore, Olivier Godet, Daniel E. Vanden Berk, Peter J. Brown, Scott Koch, David Morris, Michael Stroh, David N. Burrows, John A. Nousek, Margaret Mc Math ChesterStefan Immler, Vanessa Mangano, Patrizia Romano, Guido Chincarini, Julian Osborne, Takanori Sakamoto, Neil Gehrels

Research output: Contribution to journalArticlepeer-review

108 Scopus citations


We report me results of the Swift and XMM-Newtow observations of the Swift -discovered GRB 060729 (T90 = 115 s). The afterglow of this burst was exceptionally bright in X-rays as well as at UV/optical wavelengths, showing an unusually long slow decay phase (a = 0.14 ± 0.02), suggesting a larger energy injection phase at early times than in other bursts. The X-ray light curve displays a break at about 60 ks after the burst. The X-ray decay slope after the break is a = 1.29 ± 0.03. Up to 125 days after the burst we do not detect a jet break, suggesting that the jet opening angle is larger than 28°. We find that the X-ray spectra of the early phase change dramatically and can all be fitted by an absorbed single-power-law models or alternatively by a blackbody plus power-law model. The power-law fits show that the X-ray spectrum becomes steeper while the absorption column density decreases. In the blackbody model the temperature decreases from kT = 0.6 to 0.1 keV between 85 and 160 s after the burst in the rest frame. The afterglow was clearly detected up to 9 days after the burst in all six UVOT filters and in UVW1 even for 31 days. A break at about 50 ks is clearly detected in all six UVOT filters from a shallow decay slope of about 0.3 and a steeper decay slope of 1.3.The XMM-Newton observations started about 12 hr after the burst and show a typical afterglow X-ray spectrum with βX-1.1 and absorption column density of 1 × 1021 cm-2.

Original languageEnglish (US)
Pages (from-to)443-458
Number of pages16
JournalAstrophysical Journal
Issue number1 I
StatePublished - Jun 10 2007

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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