V. Mangano, B. Sbarufatti, V. La Parola (INAF-IASFPA),
S. T. Holland (CRESST/USRA/GSFC) report on behalf of the
Swift XRT team:
We have analysed the first two orbits of XRT data of GRB 070529
(Holland et al., GCN Circ. 6466) with total exposure time of
3.6 ks in Photon Counting mode.
The XRT position calculated on the second orbit data only,
in order to avoid pile-up effects is:
RA(J2000) = 18h 54m 58.2s
Dec(J2000) = 20d 39' 31.5"
with an uncertainty of 3.8 arcsec (radius, 90% containment).
This is 0.9 arcsec from the initial X-ray position, 69 arcsec
from the BAT refined position (Parsons et al., GCN Circ. 6468),
and 2.3 arcsec from the UVOT position (Holland et al.,
GCN Circ. 6466).
The XRT light curve follows a power-law decay with index
0.91 � 0.05 up to T+7 ks.
We extracted a spectrum of the PC data which can be fitted
with an absorbed power law with photon index of 2.2 � 0.2
and column density of (3.5+/-0.8) E21 cm-2, slightly in
excess with respect to the Galactic absorption column
(1.9E21 cm-2; Dickey & Lockman, 1990).
The absorbed (unabsorbed) 0.3-10.0 keV average flux
in the T+150 s - T+7 ks time interval is
1.6E-11 (2.8E-11) ergs cm-2 s-1.
Assuming that the source continues its decay at the present rate,
we predict an XRT count rate of 8.6E-3 counts/s at T+24 h, which
corresponds to an observed flux of 7E-13 ergs cm-2 s-1.
This circular is an official product of the Swift XRT team.