[vsnet-grb-info 6239] Swift observations of BAT Slew Survey event (Trigger=010)

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7868
SUBJECT: Swift observations of BAT Slew Survey event (Trigger=010)
DATE:    08/06/11 14:43:43 GMT
FROM:    Phil Evans at U of Leicester  <pae9 at star.le.ac.uk>

E. Troja (U. Leicester/INAF-IASFPA), S. T. Holland (CRESST/USRA/GSFC),
A. Copete (Harvard), J. Grindlay (Harvard), K. L. Page (U. Leicester),
P. A. Evans (U. Leicester), S. Barthelmy (GSFC) report:


At 09:50:17 UT on 2008-06-02, BAT detected a source during a spacecraft
slewing interval (when normal BAT triggering is disabled). This event
(ID Num=010) was detected using the BAT Slew Survey (BATSS) method.
The location is
    RA(J2000) = 00h 17m 41s
   Dec(J2000) = +48d 34m 12s
with an uncertainty of 6.3 arcmin.
This was initially distributed as a GCN/BAT_SLEW_POS Notice at 21:12 UT,
11.3 hrs after the slew.

A 6 ks ToO observation of the location started at 22:01 UT, 12.2 hrs
after the slew. XRT observation revealed a faint source (~3 x 10-3 cts/s)
with a possible fading behavior. This source is located at :

RA(J2000)= 00h 18h 05.37s
Dec(J2000)=+48d 38h 29.4s

with an uncertainty of 8.6 arcsec (90% confidence). No other candidate
afterglow was found, down to a 3 sigma upper limit of 3 x 10-3 cts/s.

UVOT observations detected two sources within the XRT error circle, whose
positions are consistent with catalogued objects. The colours of these
sources are:

(v-b)_0 = 0.76, (u-b)_0 = 0.51, suggestive of a G2I star
(v-b)_0 = 0.48, (u-b)_0 =-0.45

The colours have been corrected for the Galactic reddening of
E(B-V)=0.11 mag along the line of sight (Schlegel et al., 1998). No
evidence for variability is observed in either of these sources, and it
is not possible to determine whether one of them is the counterpart of the
XRT source.

In order to check the variability of the XRT source, further observations
with Swift were performed. The source is not detected in 6 ks of exposure,
taken from 2.6 d to 3.5 d after the slew. In later observations,
taken from 7.6 d to 8.1 d after the slew (6 ks of exposure in PC mode),
the X-ray source is clearly detected at a count rate of
(2.2+/-0.7) x 10-3 cts/s, consistent with the first detection.

We conclude that this source is unassociated to the BATSS event.