TITLE:   GCN CIRCULAR
NUMBER:  21169
SUBJECT: GRB 170519A: CrAO optical observations
DATE:    17/05/30 20:33:55 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

E. Mazaeva (IKI), K. Antonyuk (CrAO), I. Nikolenko (CrAO), V. Rumyantsev 
(CrAO),  A. Volnova (IKI), A. Pozanenko (IKI) report on behalf of larger 
GRB follow-up collaboration:

We observed the field of the GRB 170519A (Ukwatta et al., GCN 21106)
with AZT-11 telescope of CrAO observatory starting on May 19 (UT)
19:07:44, and with Zeiss-1000/Koshka telescope of Simeiz branch of CrAO
observatory starting on May 19 (UT) 19:28:57. We took several images in 
filter R with exposures of 180 s. We clearly detect the afterglow 
(Ukwatta et al., GCN 21106; Izzo et al., GCN 21108) in combined images.

Preliminary photometry of the combined images is following

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


19:07:44   0.58810	R	6*180    19.17   0.11   20.9  AZT-11
19:26:08   0.59878	R	4*180    19.23   0.12   20.7  AZT-11
19:41:28   0.61473	R	9*180    19.58   0.12   21.1  AZT-11
19:28:57   0.59751	R	1*180    19.05   0.10   20.4  Zeiss-1000
19:31:58   0.60066	R	2*180    19.12   0.10   21.1  Zeiss-1000
19:38:02   0.60592	R	3*180    19.52   0.14   20.3  Zeiss-1000
19:47:08   0.61224	R	3*180    19.52   0.16   20.3  Zeiss-1000
19:56:13   0.62065	R	5*180    19.64   0.14   21.3  Zeiss-1000

The photometry is based on nearby SDSS stars:

SDSS-DR9_id	    R(Lupton)
J105339.53+252259.9 17.32
J105332.97+252127.3 16.22		
J105348.21+252041.2 17.03			
J105341.14+252534.0 16.18				
J105353.70+252400.0 15.30