[vsnet-grb-info 19946] GRB 171020A: LT observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22033
SUBJECT: GRB 171020A: LT observations
DATE:    17/10/21 06:30:48 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:

The 2-m Liverpool Telescope automatically began observing Swift GRB 
171020A (Page et al. GCN 22028) on October 20, 23:10:12 UT (3.0 minutes 
from the GRB trigger time) with the RINGO3 polarimeter and the IO:O 
camera in the SDSS-R filter. We clearly detect the optical afterglow 
(Malesani et al, GCN 22029; Moskvitin et al., GCN 22031) with the 
following magnitude:

Mid Time      Exposure       Filter       Magnitude (AB)
(min)           (s)
-------------------------------------------------------
35.8            6x10         SDSS-R       21.12 +- 0.14
-------------------------------------------------------

as calibrated against nearby Pan-STARRS objects.