[vsnet-grb-info 19972] GRB 171027A: LCO 1-m telescope observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22059
SUBJECT: GRB 171027A: LCO 1-m telescope observations
DATE:    17/10/27 11:51:22 GMT
FROM:    Cristiano Guidorzi at Ferrara U,Italy  <guidorzi at fe.infn.it>

C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell (U. Bath), 
A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU) on behalf of a large 
collaboration report:

We began observing Swift GRB171027A (D'Avanzo et al. GCN 22053) on 
October 27, from 08:39:29 to 09:06:37 UT (16 minutes since the GRB 
trigger time) with one of the 1-m LCO McDonald telescopes in the SDSS 
gri filters. Within the enhanced Swift-XRT error circle (Evans et al. 
22054) and in particular at the position of the NIR afterglow candidate 
(Watson et al. GCN 22057) we do not see any optical source down to the 
following limits in agreement with previous reports (Lipunov et al. GCN 
22055; Schady et al. GCN 22056):

Mid Time     Exposure       Filter       Magnitude (AB)
(hrs)         (s)
-------------------------------------------------------
0.5          5x60           SDSS-G          > 19.5
0.5          5x60           SDSS-R          > 19.3
0.5          5x60           SDSS-I          > 18.8
-------------------------------------------------------

as calibrated against nearby USNO URAT1 objects.