GCN Circular 10727
Subject
GRB 100418A: Keck imaging
Event
Date
2010-05-07T23:19:17Z (15 years ago)
From
Daniel Perley at U.C. Berkeley <dperley@astro.berkeley.edu>
D. A. Perley, S. B. Cenko, A. A. Miller, D. Poznanski, A. V. Filippenko,
J. S. Bloom (UC Berkeley), and P. Nugent (LBNL) report:
We imaged the field of GRB 100418A (Marshall et al., GCN 10612) with the
Low Resolution Imaging Spectrometer on the Keck I 10-m telescope during
morning twilight on 2010-05-06 UT. Two exposures of 380 seconds each
were acquired in the g and R bands simultaneously. The midpoint of the
observation was 14:54 UT, 17.739 days after the GRB.
At the position of the afterglow and calibrating to 9 nearby unsaturated
SDSS stars, we measure magnitudes of:
g = 22.67 � 0.07
R = 21.85 � 0.05
The g-band magnitude is marginally consistent with the SDSS magnitude
(Malesani et al., GCN 10621) of g = 22.89 � 0.17, and suggests that the
UVOT flattening (Marshall et al., GCN 10720) is primarily due to the
host galaxy, not an associated supernova. Our reported R-band magnitude
is significantly brighter than the host, but this excess is consistent
with an afterglow origin (Bikmaev et al., GCN 10726). Additional
follow-up observations will be necessary to comment on the presence (or
absence) of a supernova counterpart.