TITLE:   GCN CIRCULAR
NUMBER:  6652
SUBJECT: GRB 070714B:  Keck observations
DATE:    07/07/22 20:15:47 GMT
FROM:    Daniel Perley at U.C. Berkeley  <dperley@astro.berkeley.edu>

GRB 070714B:  Keck late-time observations

D. A. Perley, J. S. Bloom (UC Berkeley), C. Thoene (DARK, UCB), and N. R.
Butler (UC Berkeley) report:

On the night of 2007 July 18 (UT) we observed the field of GRB 070714B
with the 10m Keck I Telescope (+LRIS) for 780 seconds in R and 920 seconds
in g', starting at 14:30 UT.  We detect a single, very faint source
consistent with the position reported by Melandri et al. (GCN 6621) and
inside the refined (GCN 6627) and improved [1] XRT error circles, in both
filters.  The location of this source is:

RA = 03:51:22.23
Dec = +28:17:50.8

(+/- 0.4")

The object has an approximate magnitude of R~25.5, calibrating relative to
the USNO-B2.0 star at (03:51:21.5973, +28:18:55.810).  It does not appear
visibly extended in our imaging.  This rules out the presence of a bright
host galaxy and, comparing to the magnitude reported by Levan et al. (GCN
6630) suggests a rapid late-time afterglow decay rate of the afterglow.


[1] http://astro.berkeley.edu/~nat/swift/xrt_pos.html