TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3585 SUBJECT: GRB050709: Candidate X-ray Afterglow from Chandra DATE: 05/07/13 08:36:41 GMT FROM: Derek Fox at CIT D.B. Fox (Caltech), D.A. Frail (NRAO), P.B. Cameron (Caltech), and S.B. Cenko (Caltech) report on behalf of the Caltech-NRAO-Carnegie GRB Collaboration: "We have observed the HETE localization region for GRB050709, a likely short-hard gamma-ray burst (Butler et al., GCN 3570) with the Chandra X-ray Observatory + ACIS, in a single 44 ksec observation beginning at 2005 July 12.2 UT (mean epoch 2.52 days after the burst). Excluding intervals of significant background flares, we retain 38.4 ksec good time. Performing a standard "wavdetect" analysis, we identify three sources within the SXC error circle. The fainter two of these sources are very close to each other and are coincident with the bright radio (NVSS/20-cm and 8.5 GHz) source identified by Cameron & Frail (GCN 3578). The brightest source within the error circle has a total of 49.5 +/- 8.8 counts (0.3-8.0 keV) and is located at: RA 23:01:26.96, Dec -38:58:39.5 (J2000), where we have made a slight (0.4") adjustment to the native astrometry based on the optical/X-ray coincidence of three other sources in the field, and estimate our positional uncertainty as less than 0.5". This position is ~1" distant from an R~20.5 mag point-like object visible in images from the Digitized Sky Survey. Given that our position is marginally consistent with this object, and that we cannot at this time demonstrate significant fading behavior, we caution observers that the source could be revealed to be a coronally-active star or AGN. Nonetheless, we consider it a reasonable afterglow candidate; in particular, the X-ray flux (~8.4E-15 erg/cm2/s, 2-10 keV) is consistent with a ~t**(-1.4) power-law decay from the afterglow peak observed by the SXC (assuming this peak reached ~3E-10 erg/cm2/s, 2-10 keV, at 100 sec after the burst); this flux and decay rate would also be consistent with the Swift XRT non-detection (Morgan et al., GCN 3577). A particularly intriguing prospect given observations of the short-hard burst GRB050509B (Barthelmy et al., GCN 3385; Prochaska et al., GCN 3390) is that the DSS object 1" distant from this candidate afterglow may be the burst host galaxy."