Late-time observations of the X-ray afterglow of GRB 060729

Dirk Grupe
2012 Proceedings of Gamma-Ray Bursts 2012 Conference — PoS(GRB 2012)   unpublished
We summarize the results of the late-time Chandra observations of the X-ray afterglow of the Swift-discovered GRB 060729. These Chandra observations have been the latest X-ray detections of an afterglow, even up to 21 month after the trigger. The last two Chandra observations in December 2007 and May 2008 suggest a break at about a year after the burst, implying a jet halfopening angle of about 14 degrees, if interpreted as a jet break. As an alternative this break may have a spectral origin.
more » ... spectral origin. In that case no jet break was observed and the half-opening angle is larger than 15 degrees for a wind medium. Comparing the X-ray afterglow of GRB 060729 with other bright X-ray afterglows we discuss why the afterglow of GRB 060729 was such an exceptionally long-lasting event. The detection by Chandra in May 2008 was the latest detection of an X-ray afterglow at cosmological distance ever. Figure 1: Swift XRT (black crosses) and Chandra ACIS-S (red triangles) light curve of the X-ray afterglow of GRB 060729. The solid line displays an initial decay slope of 1.32 ([2]), the dashed line the decay slope of 1.61 post-break at 1 Ms after the burst and the doted line the steep decay slope of 4.65 after the break at 41 Ms after the burst ([3]).
doi:10.22323/1.152.0079 fatcat:txowtllglvazbffogdxq5u7lna