GCN Circular 4862

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
Not found
 
 
 (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.