[vsnet-grb-info 10980] GRB 110928A: Swift-XRT observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  12398
SUBJECT: GRB 110928A: Swift-XRT observations
DATE:    11/09/28 03:51:12 GMT
FROM:    Phil Evans at U of Leicester  <pae9 at star.le.ac.uk>

P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), D.N. Burrows
(PSU), J.A. Kennea (PSU), S. Campana (INAF-OAB) and G. Cusumano
(INAF-IASF PA) report on behalf of the Swift-XRT team:

The XRT began observing the field of GRB 110928A at 02:47:09.1 UT,
3337.3 seconds after the BAT trigger. Using promptly downlinked data we
find an uncatalogued X-ray source located at RA, Dec 257.73360,
36.53636 which is equivalent to:
   RA(J2000)  = 17h 10m 56.06s
   Dec(J2000) = +36d 32' 10.9"
with an uncertainty of 4.3 arcseconds (radius, 90% containment). This
location is 136 arcseconds from the BAT onboard position, within the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
http://www.swift.ac.uk/sper.  We cannot determine whether the source is
fading at the present time. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (3.14 x
10^20 cm^-2, Kalberla et al. 2005), with an excess column of 2.1
(+2.44/-1.70) x 10^22 cm^-2 (90% confidence).