[vsnet-grb-info 19486] GRB 170519A: Mondy optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21206
SUBJECT: GRB 170519A: Mondy optical observations
DATE:    17/06/05 19:07:17 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

E. Mazaeva (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), A. Volnova (IKI) 
report on behalf of larger GRB follow-up collaboration:

We observed the field of GRB 170519A (Ukwatta et al., GCN 21106) with
AZT-33IK telescope of Sayan observatory (Mondy) starting on May 20 (UT) 
16:27:01. We took several images in R-filter with exposures of 120 s. 
The optical afterglow (Ukwatta et al., GCN 21106; Izzo, et al., GCN 
21108) is clearly visible in single images.

We continued our observations on May 27 (UT) 16:28:02, i.e., ~8.5 days
after the BAT trigger. We took several R-filtered images. We do not 
detect the optical counterpart in the enhanced XRT error circle 
(Beardmore et al., GCN 21107).

Preliminary photometry of the afterglow is following:

Date       UT start   t-T0    Filter  Exp.     OT     Err.     UL
                                    (mid, days)      (s) 
        (3 sigma)

2017-05-20 16:27:01  1.47708  R   10*120  19.99 0.03 22.8
2017-05-20 17:07:02  1.50487  R   10*120  19.99 0.03 22.6
2017-05-27 16:28:02  8.49905  R   39*120  n/d   n/d  22.6

The photometry is based on nearby SDSS stars reported by
Mazaeva et al. (GCN 21169).