[vsnet-grb-info 5699] GRB080229B: Swift XRT afterglow observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7354
SUBJECT: GRB080229B: Swift XRT afterglow observation
DATE:    08/03/03 11:53:47 GMT
FROM:    Alberto Moretti at Obs Brera Merate  <alberto.moretti at brera.inaf.it>

A. Moretti (INAF-OAB), J. Mao (INAF-OAB), C. Guidorzi
(Univ. Bicocca & INAF-OAB) report on behalf of the Swift-XRT team:

We have analysed the Swift-XRT observation of GRB 080229B detected by
SuperAgile (Evangelista et al. GCN Circ).  The data consist of 13.4 ks
in Photon Counting (PC) mode starting 27 hours after the SuperAGILE
trigger and ending at 48 hours.

We found a fading, uncatalogued X-ray source at the position: RA:199.25169
Dec:-64.86239 which is equivalent to:

   RA(J2000)  = 13h 17m 00.40s
   Dec(J2000) = -64d 51' 44.6"

with an uncertainty of 3.9 arcseconds (radius, 90% containment). This
location is 73 arcseconds from the SuperAGILE position.

The afterglow is decaying with a power-law slope of 0.9+/-0.5.  

The spectral parameters are poorly constrained due to the paucity of
the statistics (~100 photons).  The spectrum can be modelled with a
power-law of photon index Gamma = 2.8 +/- 1.0, with an absorbing
column of NH = (1.4 +/- 0.7)e22 cm^-2 (consistent with the
Galactic value of 8.9e21 cm^-2).

If the light-curve continues to decay with a slope of 0.9, the
afterglow at 3 days (March 4th) will have an expected count rate of
0.0085 count s-1. This corresponds to an observed (unabsorbed)
flux of 5.8E-13 (2.2e-12) ergs cm-2 s-1.

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