TITLE:   GCN CIRCULAR
NUMBER:  6503
SUBJECT: GRB 070611: Swift-XRT refined analysis
DATE:    07/06/11 18:10:42 GMT
FROM:    Michael Stroh at PSU/Swift  <stroh@astroh.org>

M.C. Stroh, C. Pagani & J. Racusin report on behalf of the Swift XRT team:

We have analysed the first four orbits of XRT data of GRB 070611 (Stroh et
al., GCN Circ. 6494) with total exposure time of 8.9 ks in Photon Counting
mode. The calculated XRT position is RA(J2000) = 1.9927, Dec (J2000) =
-29.7557, corresponding to:
RA(J2000)  = 00h 07m 58.3s
Dec(J2000) = -29d 45' 20.4"

with an uncertainty of 4.0 arcsec (radius, 90% containment). This is 6.1
arcsec from the initial XRT position, and 3.4 arcsec from the ROTSE-III
optical candidate reported by Rykoff, et al. (GCN Circ. 6497).

The XRT light curve follows a power-law decay with index 0.83 +/- 0.27
continuing through T+30 ks.

The PC spectrum can be fit with an absorbed power law with photon index of
1.9 +/- 0.5 and column density of (5 +/- 5) E20 cm-2, consistent with the
Galactic absorption column density (1.34E20 cm-2; Dickey & Lockman, 1990).

The absorbed (unabsorbed) 0.3-10.0 keV average flux in the T+3 ks - T+30
ks time interval is 6.056E-13 (6.825E-13) ergs cm-2 s-1.

Assuming that the source continues its decay at the present rate, we
predict an XRT count rate of 4.9E-3 counts/s at T+24 h, which corresponds
to an absorbed (unabsorbed) flux of 2.144E-14 (2.417E-14) ergs cm-2 s-1.

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