TITLE:   GCN CIRCULAR
NUMBER:  21162
SUBJECT: GRB 170519A: ISON/Multa optical observations
DATE:    17/05/29 18:41:18 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

E. Mazaeva (IKI), A. Krylov (KIAM), Yu. Krylova (KIAM), S. Schmalz 
(KIAM), A. Volnova (IKI), A. Pozanenko (IKI) report on behalf of larger 
GRB follow-up collaboration:

We observed the field of GRB 170519A (Ukwatta et al., GCN 21106) with 
22cm SSS-220 telescope of ISON/Multa observatory(* starting on May 19 
(UT) 16:02:54. We took 120 unfiltered frames with 60 s exposure. The 
optical transient (Ukwatta et al., GCN 21106; Izzo, et al., GCN 21108) 
is clearly detected in a combined image.

Preliminary photometry of the combined image is following

Date        UT start  t-T0     Filter  Exp.   OT     err   UL
                       (mid, days)      (s)               (3sigma)
2017-05-19  16:02:54  0.53936  CR      120*60 18.92  0.28 19.0	

The photometry is based on nearby SDSS stars:

SDSS-DR9_id         R(Lupton)
J105316.02+252545.1 16.75
J105332.97+252127.3 16.22
J105336.13+251707.2 15.46
J105322.03+251651.0 15.91
J105339.27+251620.6 16.66
J105338.87+252621.2 16.00

*) The ISON/Multa observatory is located in Altai, N 50d 10′ 07″ E 85d 
57′ 25″. The SSS-220  telescope (22 cm, f/2.3) is equipped with CCD 
camera ML 11002.