[vsnet-grb-info 6182] GRB 080603B: Swift-XRT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7811
SUBJECT: GRB 080603B: Swift-XRT refined analysis
DATE:    08/06/04 16:37:24 GMT
FROM:    Boris Sbarufatti at INAF-IASF-Pa  <sbarufatti at ifc.inaf.it>

V. Mangano, V. La Parola, B. Sbarufatti (INAF-IASF PA) report on behalf
of the Swift-XRT team:

The Swift-XRT observed GRB 080603B (trigger 313087, Mangano et
al. GCN Circ 7794) for three orbits which consisted of 200 s of
Windowed Timing mode data starting 68 s after the trigger and
990 s of Photon Counting mode data, 274 s after the trigger.

We obtained a refined XRT position at
RA, Dec = 176.53312  68.06058 which is equivalent to:

RA (J2000):  11 46 07.95
Dec (J2000): 68 03 38.11

with an uncertainty of 3.7 arcsec (radius, 90% confidence).
The position is 3.2 arcsec from the on-board position reported
in GCN Circ. 7794 and 0.7 arcsec from the refined UVOT position
(Kuin et al. GCN Circ 7808).

The X-ray light curve shows an initial steep decay with a slope
of 3.4 ± 0.1, breaking to a shallower decay of 0.8 ± 0.1  at
a time of 161 ± 6 s after the trigger.

A spectrum of the Windowed Timing data can be well fit by an absorbed
power-law, with a photon index Gamma = 1.68 ± 0.06 and a column
density Nh = (7.9 ± 0.2) e21 cm-2 in excess with respect to the Galactic
column density in this direction of 1.2e20 cm-2. The observed
(unabsorbed) 0.3-10 keV flux is 7.0e-10 (7.7e-10) erg cm-2 s-1.

The Photon Counting mode spectrum is also well fit by an absorbed
powerlaw, with an Nh = (1.3 ± 0.2) e22 cm-2 and Gamma = 2.0 ± 0.2.
The observed (unabsorbed) 0.3-10 keV flux is 1.55 e-11 (1.91e-11)
erg cm-2 s-1.

The predicted XRT count rate after 24 hours from burst is 6.0e-2 counts/s

This circular is an official product of the Swift-XRT team.