[vsnet-grb-info 4775] GRB070612B: P60 Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6517
SUBJECT: GRB070612B: P60 Observations
DATE:    07/06/12 08:56:35 GMT
FROM:    S. Bradley Cenko at Caltech  <cenko at srl.caltech.edu>

S. B. Cenko, A. Rau (Caltech) and D. B. Fox (Penn State) report on behalf
of a larger collaboration:

We have imaged the field of GRB070612B (Grupe et al., GCN 6511) with the
automated Palomar 60-inch telescope.  Images were taken in the Kron R and
Sloan i' and z' filters beginning approximately 12 minutes after the
burst.

We find no sources inside the XRT error circle (Grupe and Evans, GCN
6514).  Photometric calibration for the limits below was performed using
USNO B-1 mangitudes converted to the SDSS photometric sytem using
empirical relations from Jordi, Grebel & Ammon (A&A 460, 339, 2006):

t_b (min.)		Filter		Mag. Limit
-----------------------------------------------------------------------
21.2			i'		> 21.0
22.7			z'		> 20.5

We marginally detect a source just outside of the XRT error circle in our
i' coaddition.  The source, with i' magnitude ~ 22.0, is located at
coordinates (J2000.0):

	RA: 17:26:54.936
	Dec: -08:45:08.35

This source is not present in either our R- our z'-band imaging of
this field.  Because of the faintness, we cannot assess the variability
of this source at the present time.