GCN Circular 12388
Subject
GRB110918A: Lick Observations
Date
2011-09-23T01:36:34Z (13 years ago)
From
Daniel Perley at U.C. Berkeley <dperley@astro.berkeley.edu>
D. A. Perley (Caltech), M. Ganeshalingam, P. Blanchard, and M. Mason (UC
Berkeley) report:
We observed the location of bright IPN GRB 110918A (Hurley et al, GCN
12357) starting at UT 2011-09-22 03:04:29 UT using the Nickel 40-inch
telescope at Lick Observatory, under good seeing conditions at high
airmass. A series of five 180-second exposures in R-band were acquired
in total. The optical afterglow (Tanvir et al., GCN 12365) is
well-detected in the combined stack. Using five nearby USNOB1.0 stars,
we calculate the following photometry:
R = 20.68 +/- 0.13 (t_mid = 3.2406 day)
The uncertainty estimate does not include the uncertainty of the
calibration to USNO (for convenience, our calibration stars are listed
below). The measurement indicates a decay slope of approximately
alpha=2.2 since the report of Guidorzi et al. (GCN 12382) and may
suggest a very early jet break for this burst (see also Cenko et al.,
GCN 12367).
USNO calibration stars:
RA dec R2
032.546809 -27.104117 19.38
032.549492 -27.121698 19.29
032.555214 -27.117650 19.38
032.558045 -27.100853 19.39
032.569403 -27.106270 19.40