[vsnet-grb-info 21014] GRB 180809B: LCO Sutherland observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23112
SUBJECT: GRB 180809B: LCO Sutherland observations
DATE:    18/08/10 08:59:56 GMT
FROM:    Cristiano Guidorzi at Ferrara U,Italy  <guidorzi at fe.infn.it>

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

We observed Swift GRB 180809B (Moss et al. GCN 23105) with the LCO 1-m 
units at Sutherland Observatory (South Africa) on August 09, from 20:58 
to 22:29 UT (corresponding to 0.5 to 2.0 hours from the GRB trigger 
time) with the SDSS r' and i' filters. We clearly detect the optical 
afterglow (Moss et al; Lipunov et al. GCN 23109; Watson et al. GCN 
23110; Schweyer et al. GCN 23111) in both filters with the following 
magnitudes:

Mid time from GRB      Exposure         Filter Magnitude
trigger time (hrs)     (s)
---------------------------------------------------------------------
0.55                   5x60             SDSS r'         19.54 +- 0.08
0.70                   5x60             SDSS i'         19.24 +- 0.07
---------------------------------------------------------------------

as calibrated against nearby Pan-STARRS objects.