GCN Circular 15319
Subject
GRB 131004A: MOSFIRE NIR imaging
Date
2013-10-08T09:31:30Z (11 years ago)
From
Daniel Perley at Caltech <dperley@astro.caltech.edu>
D. A. Perley (Caltech) reports:
I imaged the location of GRB 131004A (GCN 15303) in Ks-band with MOSFIRE
on the Keck I telescope on the night of 2013-10-07 for a total
integration time of 291 seconds under good seeing conditions but some
cloud cover. The midpoint of the integration was 07:21 UT, 2.40 days
after the GRB.
At the location of the optical transient reported by Xu et al. (GCN
15304), no source is detected to a limiting magnitude of Ks > 20.6. The
nearest detected object to this location is a faint (Ks = 19.7), compact
source approximately 1.4 arcsec to the west, at RA=19:44:26.99,
dec=-02:57:30.15.
Given the moderate redshift of z=0.717 (Chornock et al., GCN 15307),
these results suggest either that the host of this event is a relatively
low-mass galaxy or that the GRB exploded outside the bulk of the stellar
light of its host. The >1.5 sec duration and significant lag reported
in the BAT refined analysis (Lien et al., GCN 15316) may suggest the
former interpretation is more likely.
I thank D. Malesani for providing the NOT image to verity the location
of the optical transient.