TITLE:   GCN CIRCULAR
NUMBER:  20593
SUBJECT: GRB 170202A: LCO FTN observations
DATE:    17/02/03 11:36:23 GMT
FROM:    Cristiano Guidorzi at Ferrara U,Italy  <guidorzi@fe.infn.it>

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

We observed Swift GRB 170202A (Racusin et al. GCN 20575) on February 03, 
from 10:30 to 10:40 UT (16 hours since the GRB) with the 2-m LCO FTN in 
Hawaii with SDSS r and i filters. We detect the optical afterglow with 
the following values:

Mid Time      Exposure       Filter       Magnitude (AB)
(hours)           (s)
-------------------------------------------------------
16.1            2x120         SDSS-R      21.10 +- 0.15
16.2            2x120         SDSS-I      20.94 +- 0.19
-------------------------------------------------------

as calibrated against nearby SDSS sources.