[vsnet-grb-info 4764] GRB 070610: Swift-XRT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6506
SUBJECT: GRB 070610: Swift-XRT refined analysis
DATE:    07/06/11 21:11:43 GMT
FROM:    Claudio Pagani at PSU/Swift-XRT  <pagani at astro.psu.edu>

C. Pagani, J. L. Racusin and J. A. Kennea (PSU) report on  
behalf of the Swift Team:

We have analysed the first 7.8 ks of Swift XRT photon counting mode data from 
GRB 070610 (trigger number 281993, GCN Circ. 6489).
Because of an Earth limb constraint, the spacecraft did not slew promptly to 
the BAT position and the XRT started collecting data in Photon Counting at 
21:44:41 UT, 3140 seconds after the trigger.

Using 299 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=
298.79002, 26.2352 which is equivalent to:

RA (J2000):  19 55 9.60
Dec (J2000): +26 14 06.7

with an uncertainty of 4.3 arcsec (90% confidence).
This is 0.4 arcsec from the initial X-ray position (GCN Circ. 6490), 1.7 
arcsec from the OSN optical candidate (GCN Circ. 6501) and 89 arcsec from the 
BAT ground-calculated position (GCN Circ. 6491).

The XRT light curve created from the PC data in the T+3.1 ks to T+69 ks time 
interval does not show the typical afterglow fading behavior, with evidence 
of flaring activity and hints of a possible late rebrightening.  More data 
are being collected to monitor the light curve evolution.

The X-ray spectrum of the PC data, modeled with an absorbed power law with the 
total column density fixed at the Galactic value of 1.01e22 cm**-2 gives a 
photon index of 2.1+/-0.5. 
The absorbed (unabsorbed) 0.3-10.0keV average flux in the T+3.1 ks - T+69 ks 
time interval is 1.4E-12 (2.9E-12) ergs cm^-2 s^-1.

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