TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4862 SUBJECT: GRB 060312: Swift XRT team refined analysis DATE: 06/03/12 08:30:49 GMT FROM: Dirk Grupe at PSU/Swift-XRT Subject: GRB 060312: Swift XRT team refined analysis Dirk Grupe (PSU), David N. Burrows (PSU), Claudio Pagani (PSU), on behalf of the Swift XRT team: We report on the analysis of the first three orbits of X-ray data of the Swift discovered GRB 060312. The XRT began observing the field of GRB 060312 01:36:12 UT, 51 seconds after the BAT trigger. The following refined position was obtained: RA(J2000) = 03h 03m 06.12s Dec(J2000)= =12d 50' 03.5" with an estimated uncertainty of 3.7 arcsec (90% containment). This is 0.5 arcsec from the XRT position given in GCN 4859 (Grupe et al.), and 87 arcsec from the BAT position reported in the same circular. The X-ray spectrum of the Windowed Timing (WT) data can be fitted by a single absorbed power low with a photon index Gamma=2.17+/-0.10 and an absorption column density NH=(2.3+/_0.3)e21 cm-2. This column density is above the Galactic value (1.4e21; Dickey & Lockman 1990) and suggests that the burst is intrinsically absorbed. The photon counting (pc) mode data are consistent with this result. The light curve shows several flares in the first orbit. The underlying afterglow decay slope withing the first 10 ks after the burst is alpha=0.60+/-0.13. Assuming this decay slope the prediction for the flux 24 hours after the trigger is 4e-13 ergs/s/cm2. This circular is an official product of the Swift-XRT team.