[vsnet-grb-info 3374] GRB 060602B: Swift-XRT Refined Analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  5209
SUBJECT: GRB 060602B: Swift-XRT Refined Analysis
DATE:    06/06/04 00:33:38 GMT
FROM:    Andy Beardmore at U Leicester  <apb at star.le.ac.uk>

A.P. Beardmore, O. Godet (U. Leicester) and T. Sakamoto  (GSFC/ORAU) 
report on behalf of the Swift-XRT team :

We have analysed the first 11.4ks of Swift XRT PC mode data from the BAT
trigger GRB060602B (Schady et al., GCN 5200; trigger number 213190). We 
find a refined XRT position of:

RA(J2000)  =  17:49:31.6
Dec(J2000) = -28:08:03.2

with an estimated uncertainty of 3.7 arcsec (90% containment). This is
1.4 arcsec away from the XRT position reported in GCN 5200 and 64.2 
arcsec from the refined BAT position (Palmer et al., GCN 5208).

The X-ray light curve shows a small rise in intensity until T+200s, then 
follows a simple power-law decay with a index of 1.05 +/- 0.07.

The X-ray spectrum over the same interval (T+100s to T+40ks) can be well 
modelled by an absorbed power-law, with a photon index of 3.1 +/- 0.6 
and a column density of 5.0 +/- 1.4 E22 cm^-2. The measured galactic 
column density in this direction is 1.4E22 cm^-2. The observed 0.3-10keV 
flux is 3.2E-12 ergs cm**-2 s**-1, which corresponds to an unabsorbed 
flux of 5.0E-11 ergs cm**-2 s**-1. The measured spectral and temporal 
indices are difficult to reconcile with standard GRB afterglow models.

The X-ray spectrum can also be equally well fit by an absorbed blackbody 
model, with a temperature of 0.90+/-0.09 keV and a column density of 2.1 
+/- 0.7 E22 cm^-2. This model has an observed (unabsorbed) 0.3-10 keV flux 
of 2.8E-12 (4.3E-12) ergs cm**-2 s**-1.

Assuming the source decays at the same rate, we predict an XRT count 
rate of 0.0011 count/s at T+48 hrs, which corresponds to an  observed 
flux of 8.8E-14 ergs cm**-2 s**-1.

This Circular is an official product of the Swift XRT Team.