GCN Circular 17707
Subject
GRB 150413A: additional P60 observations
Event
Date
2015-04-15T11:29:50Z (11 years ago)
From
Daniel Perley at Caltech <dperley@astro.caltech.edu>
D. A. Perley (Caltech) and S. B. Cenko (GSFC) report:
We have continued to follow the optical counterpart of GRB 150413A
(Markwardt et al., GCN 17688; Ivanov et al., GCN 17689) with the
Palomar 60-inch robotic telescope. A second griz epoch was acquired
between 10:08:52 and 10:49:31 UT on the night of 2015-04-14, followed by
two deeper epochs (one gri, one r only) on the night of UT 2015-04-15.
Calibrating our r-band observations to a common set of USNO R-band
reference stars, we derive the following photometry (statistical
uncertainties only):
dt_mid = 0.5602 day : R = 19.13 +/- 0.03
dt_mid = 0.8464 day : R = 20.23 +/- 0.06
dt_mid = 1.6034 day : R = 21.52 +/- 0.16
dt_mid = 1.8652 day : R = 21.74 +/- 0.18
This suggests steep decay over this period (decay index ~ 2.2).