TITLE:   GCN CIRCULAR
NUMBER:  21991
SUBJECT: GRB 171010A: LCO 1m telescope observations
DATE:    17/10/11 14:17:15 GMT
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) on behalf of a large 
collaboration report:

We began observing Fermi LAT GRB 171010A (Omodei et al. GCN 21985) on 
October 11, from 02:15 to 02:28 UT (7.2 hours since the GRB trigger 
time) with one of the 1-m LCO telescopes in Sutherland in the SDSS-I 
filter. Within the enhanced Swift-XRT circle (D'Ai et al. GCN 21989) we 
clearly detect the optical afterglow (Thorstensen and Halpern, GCN 
21987; Izzo and Malesani, GCN 21988) with the following magnitude:

Mid Time����� Exposure������ Filter������ Magnitude (AB)
(hrs)���������� (s)
-------------------------------------------------------
7.3����������� 5x120�������� SDSS-I������ 16.82 +- 0.02
-------------------------------------------------------

as calibrated against nearby Pan-STARRS objects.