Late-time detections of the X-ray afterglow of GRB 060729 with Chandra - the latest detections ever of an X-ray afterglow

Abstract

We report on 5 Chandra observations of the X-ray afterglow of the Gamma-Ray Burst GRB 060729 performed between 2007 March and 2008 May. In all five observations the afterglow is clearly detected. The last Chandra pointing was performed on 2008-May-04, 642 days after the burst - the latest detection of a GRB X-ray afterglow ever. A reanalysis of the Swift XRT light curve together with the three detections by Chandra in 2007 reveals a break at about 1.0 Ms after the burst with a slight steepening of the decay slope from alpha = 1.32 to 1.61. This break coincides with a significant hardening of the X-ray spectrum, consistent with a cooling break in the wind medium scenario, in which the cooling frequency of the afterglow crosses the X-ray band. The last two Chandra observations in 2007 December and 2008 May provide evidence for another break at about one year after the burst. If interpreted as a jet break, this late-time break implies a jet half opening angle of about 14 degrees for a wind medium. Alternatively, this final break may have a spectral origin, in which case no jet break has been observed and the half-opening angle of the jet of GRB 060729 must be larger than about 15 degrees for a wind medium. We compare the X-ray afterglow of GRB 060729 in a wind environment with other bright X-ray afterglows, in particular GRBs 061121 and 080319B, and discuss why the X-ray afterglow of GRB 060729 is such an exceptionally long-lasting event.

Accepted by ApJ, 12 pages, 5 figures, 2 tables, revised version

References in corpus (16)

• Methods and results of an automatic analysis of a complete sample of Swift-XRT observations of GRBs
• Gamma-Ray Bursts
• Gamma-Ray Bursts: Progress, Problems & Prospects
• Particle acceleration in relativistic collisionless shocks: Fermi process at last?
• Bayesian Estimation of Hardness Ratios: Modeling and Computations
• Jet breaks and Energetics of Swift GRB X-ray Afterglows
• Testing the standard fireball model of GRBs using late X-ray afterglows measured by Swift
• A Comprehensive Analysis of Swift/XRT Data: III. Jet Break Candidates in X-ray and Optical Afterglow Lightcurves
• The Dynamics and Afterglow Radiation of Gamma-Ray Bursts. I. Constant Density Medium
• Jet Breaks in Short Gamma-Ray Bursts. II: The Collimated Afterglow of GRB 051221A
• Swift observations of GRB 060614: an anomalous burst with a well behaved afterglow
• Swift and XMM-Newton Observations of the Extraordinary GRB 060729: An afterglow with a more than 100 days X-ray light curve
• GRB 061121: Broadband spectral evolution through the prompt and afterglow phases of a bright burst
• Jet Breaks in Short Gamma-Ray Bursts. I: The Uncollimated Afterglow of GRB 050724
• Swift Discovery of Gamma-Ray Bursts without Jet Break Feature in their X-Ray Afterglows
• Are the missing X-ray breaks in Gamma-ray Burst afterglow light curves merely hidden?

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