GCN Circular 21961
Subject
GRB 171003A: LT early optical observations
Date
2017-10-03T10:34:35Z (7 years ago)
From
Cristiano Guidorzi at Ferrara U,Italy <guidorzi@fe.infn.it>
C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell (U. Bath),
A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU), T. Laskar (UC Berkeley)
on behalf of a large collaboration report:
The Liverpool Telescope automatically began observing Swift possible GRB
171003A (Cenko et al. GCN 21960) on October 03, 02:51:26 UT (14 minutes
after the GRB trigger time) with RINGO3 polarimeter and IO:O camera in
the SDSS R filter. In addition to the presence of a couple of catalogued
bright objects, within the Swift-XRT error circle we very marginally
detect a possible faint, uncatalogued object at the following position:
RA(J2000) =� 02:43:40.65
DEC(J2000)= +61:25:53.6
at ~9" from the bright stars above mentioned, with an error radius of
about 1" and a magnitude of r'=21.3 +- 0.3 (in a 6x10s frame at 48
minutes post GRB), as calibrated against Pan-STARRS field stars. The
same possible source is not detected by us earlier, at a mid time of 19
minutes post GRB down to r'>20.5 mag. Combining the two measures, a
corresponding upper limit of alpha<0.8 is obtained on the average
power-law decay index.