TITLE:   GCN CIRCULAR
NUMBER:  6085
SUBJECT: GRB 070208: Swift XRT refined analysis
DATE:    07/02/08 23:40:46 GMT
FROM:    Maria Laura Conciatore at ASDC  <conciatore@asdc.asi.it>

M.L. Conciatore, G. Stratta, M. Perri (ASDC), G. Sato (GSFC/ISAS)
D. Burrows (PSU) report on behalf of the Swift/XRT team:

We have analysed the first seven orbits of XRT data GRB070208. A 11.7
ks photon counting mode image provides a refined XRT position:

RA(J2000) =13h 11m 32.73s,
Dec(J2000) =+61d 57m 55.20s

with an uncertainty of 3.7 arcsec (90% containment). This position is
0.3 arcsec from the XRT position quoted in Sato et el. (GCN
Circ. 6074), 72 arcsec from the ground-calculated BAT position
reported by Markwardt et al. (GCN Circ. 6081) and 1.7 arcsec from the
fading source reported by Guidorzi et al. (GCN Circ. 6077; see also
Fox et al., GCN Circ. 6078).

The 0.3-10 keV X-ray light-curve, after an initial slow rising phase,
shows a steep decay (alpha~-3.6) during the second orbit (from T+4.3ks
to T+6.7ks). Starting from the third orbit, the light-curve shows a
power-law decline with a decay index of 1.8+/-0.4.

The X-ray spectrum is well fitted by an absorbed power-law with a
photon index of 2.6 +/- 0.2 and column density of (2.6 +/-0.4 )e21
cm**-2. We note the Galactic column density in the direction of the
source is 1.7e20 cm**-2.  The 0.3-10 keV observed flux was 1.5e-12
ergs cm**-2 s**-1, which corresponds to an unabsorbed flux of 3.5e-12
ergs cm**-2 s**-1.

If the burst continues decaying at the current rate we estimate an XRT
count rate of 0.002 counts/s at T + 24hr, which corresponds to an
observed 0.3-10 keV flux of 2.3e-13 ergs cm**-2 s**-1

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