[vsnet-grb-info 5007] GRB070805 XRT and UVOT afterglow candidate

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6716
SUBJECT: GRB070805 XRT and UVOT afterglow candidate
DATE:    07/08/07 22:04:03 GMT
FROM:    Valentina La Parola at INAF-IASPA  <laparola at ifc.inaf.it>

V. La Parola, P. Schady, F.E. Marshall, S. T. Holland and 
A. M. Parsons, E. Troja, J. Kennea
report on behalf of the Swift team

We have analysed the XRT and UVOT observations of 
GRB070805 (Parsons et al., GCN 6708).

The XRT observed the BAT position twice, with 2.3 and 7.7 
ksec exposure times.
We find a faint source (estimated unabsorbed flux: 3.4e-13 
erg/s/cm2) within the BAT error circle, at
RA= 16 20 02.8 (245.01175)
Dec= -59 57 34.8 (-59.959657)
(4 arcsec error radius, 90% confidence)
that is 82 arcsec from the BAT position (Stamatikos et al, 
GCN 6711)
This source does not show any sign of decay, its count 
rate being consistent between the two observations.
The source is too faint to allow for any detailed spectral 
or temporal analysis.

A second, fainter source is detected only in the second 
observation, at
RA= 16 20 16.8 (245.069937)
Dec= -59 57 12.7 (-59.95352)
(4.7 arcsec error radius, 90% confidence)
The estimated unabsorbed flux is 1.13e-13 erg/s/cm2.

At present, neither of these sources can be confidently 
associated with the GRB afterglow.

On further inspection of the UVOT observations, an 
uncatalogued source is detected at the position of the 
first XRT source. This source was initially unidentified 
(GCN Circ. 6712) due to the density of the field and size 
of the BAT error circle. The source is detected in the 
white band filter at more than 3 sigma with an estimated 
magnitude of 20.1+/-0.2, and is marginally detected in the 
V, B and U filters. The refined UVOT coordinates of this 
source are
RA = 16 20 03.11 (245.0131)
Dec = -59 57 34.9 (-59.9597)
with an uncertainty of 0.7 arcseconds. There is little 
evidence for variability in the limited data currently 
available. Observations are ongoing.

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