[vsnet-grb-info 2616] GRB 060108: Refined XRT analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4453
SUBJECT: GRB 060108: Refined XRT analysis
DATE:    06/01/09 11:56:40 GMT
FROM:    Kim Page at U.of Leicester  <kpa at star.le.ac.uk>

K.L. Page, A.P. Beardmore, M.R. Goad, D.N. Burrows, J. Greiner (MPE) & D.  
Hinshaw (GSFC-SPSYS) report on behalf of the Swift-XRT Team:

We have analysed the first 7 orbits of X-ray data for GRB 060108. A ~9ks 
PC mode image gives a refined X-ray position of:

RA(J2000)  =  09h 48m 01.6s
Dec(J2000) = +31d 55' 04.6"

with an estimated uncertainty of 3.4" (radius, 90% containment), including 
corrections for the XRT boresight. This is 1.9" from the XRT position 
given by Page et al. (GCN 4444) and 61" from the refined 
(ground-calculated) BAT position (Sakamoto et al.; GCN 4445).

Spectra from both the first and later orbits of data are consistent with a
single power-law model, with Gamma = 1.76 +/- 0.19. There is no evidence
for absorption in excess of the Galactic value of 1.7e20 cm^-2. From the
first orbit of PC data (107-1072 seconds after the trigger), the 0.3-10
keV observed (unabsorbed) flux was calculated to be 1.08e-11 (1.13e-11) 
erg cm^-2 s^-1.

The PC light-curve shows some slight flaring activity, with the underlying 
continuum being well modelled by a broken power-law with parameters:

alpha_1 = 2.2 +/- 0.5
t_break = 280+/- 64 s
alpha_2 = 0.43 +/- 0.06

This predicts the observed (unabsorbed) flux at 24 hours after the burst
to be 9.8e-13 (1.0e-12) erg cm^-2 s^-1.