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GCN Circular 6800

GRB 070917: P60 Observations
2007-09-19T00:08:45Z (17 years ago)
S. Bradley Cenko at Caltech <>
S. B. Cenko (Caltech) reports on behalf of a larger collaboration:

We have imaged the field of GRB070917 (Cummings et al., GCN 6791) with the
automated Palomar 60-inch telescope.  Images were obtained in the Kron R
and Sloan i' filters beginning 2.65 minutes after the burst trigger under
poor seeing conditions.

Inside the XRT error circle (Evans et al., GCN 6796), we marginally detect
in both filters a single faint source not clearly visible in the DSS-II
plate at the location (J2000.0)

	RA: 19:35:40.53
	Dec: +02:24:40.4

Using several nearby stars from the USNO-B catalog for reference, and the
empirical filter transformations from Jordi, Grebel, and Ammon (A&A 460,
2006), we measure magnitudes of R ~ 22.0 mag, i' ~ 21.6 mag, with the
large uncertainties (~ 0.4 mag) due to both photometric calibration and
the faintness of object.

Given the faintness, we cannot determine at this time if this object is
variable.  Furthermore, as it likely lies below the detection limit of the
DSS-II survey, further observations are required to establish if it is
indeed the optical afterglow of GRB 070917.
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