TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2649 SUBJECT: XRF040812: possible afterglow DATE: 04/08/18 15:57:39 GMT FROM: Sergio Campana at INAF-OAB S. Campana and A. Moretti (INAF-Osservatorio di Brera) report: "We analyzed the Chandra ACIS-S data of the XRF040812 (Gotz et al. 2004, GCN 2640) region. We carried out spectral analysis of the second source (CXOJ162602.3-444349) in the Patel et al. (2004, GCN 2648), the only one with a sizable number of counts. The source is extremely hard with a photon index of 0.1+\-0.6 (90% confidence level), fixing the column density to the Galactic value of 5.3x10^21 cm-2. Leaving free the column density the error on the photon index increases to 0.1_(-1.0)^(+1.5). This hard photon index is typical of GRB X-ray afterglows. The unabsorbed 0.5-10 keV source flux is 2.53E-13 erg cm-2 s-1. The following Chandra observation (August 22, 2004) will allow to assess the afterglow nature of CXOJ162608.4-444125." We acknowledge the extraordinary effort by the CXC in providing rapid processing of this challenging data-set, thereby enabling this report. This message can be cited.