J. Racusin, J. Kennea, C. Pagani, L. Vetere (PSU), and P. Evans (U.
Leicester) report on behalf of the Swift/XRT team:
We have analyzed the first 15 ks of Swift XRT PC and WT data from GRB
070714B (Racusin et al., GCN 6620). Using 770 s of overlapping XRT Photon
Counting mode and UVOT V-band data, we find an astrometrically corrected
X-ray position (using the XRT-UVOT alignment and matching UVOT field
sources to the USNO-B1 catalogue): RA, Dec = 57.84287, 28.29782 which is
RA (J2000): 03h 51m 22.29s
Dec (J2000): +28d 17' 52.2"
with an uncertainty of 1.8 arcsec (90% confidence, radius). This is 35
arcsec from the refined BAT position (Barbier et al., GCN 6623), and 1.4
arcsec from the Liverpool optical afterglow candidate (Melandri et al.,
The XRT light curve shows a fading behavior with super-imposed small
flaring. The light curve can be fit with a power-law beginning with a
steep decay with a slope of 2.49 +/- 0.18 followed by a plateau beginning
at 413s +/- 50s with a slope of 0.60 +/- 0.29 until another break at 1187
+/- 270s with a decay of 1.73 +/- 0.11.
The X-ray PC and WT spectrum is well fit by an absorbed power law with a
photon index for 1.2 +/- 0.1 and a column density of 13 +/- 3 e20 cm^-2 in
excess of the galactic value (6.4e20 cm-2). The absorbed (unabsorbed)
0.3-10.0 keV flux of the WT spectrum is 9.2e-10 (1.0e-9) erg cm^-2s^-1 and
the flux of the PC spectrum is 3.4e-12 (3.7e-12) ergs cm^-2 s^-1.
Assuming the source continues to decay at the same rate, we predict an XRT
count rate of 2.7e-4 counts/s at T0+24 hours, which corresponds to an
observed (unabsorbed) flux of 1.8e-13 (2.0e-13) ergs cm^-2 s^-1.
This circular is an official product of the Swift XRT team.