TITLE: GCN CIRCULAR NUMBER: 21208 SUBJECT: GRB 170519A: TShAO and AbAO optical observations DATE: 17/06/05 19:41:04 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), A. Pozanenko (IKI), A. Kusakin (Fesenkov Astrophysical Institute), R. Inasaridze (AbAO), I. Reva (Fesenkov Astrophysical Institute), A. Volnova (IKI), V. Ayvazian (AbAO), O. Kvaratskhelia (AbAO), G. Inasaridze (AbAO), I. Molotov (KIAM) report on behalf of larger GRB follow-up collaboration: We observed the field of GRB 170519A (Ukwatta et al., GCN 21106) with Zeiss-1000 1-m telescope of Tien Shan Astronomical Observatory starting on May 20 (UT) 18:42:38. We took several images in R-filter with exposures of 120 s during this night and 2 subsequent nights. The optical afterglow (Ukwatta et al., GCN 21106; Izzo, et al., GCN 21108) is visible in stacked images. We also observed this field with AS-32 (0.7m) telescope of Abastumani Observatory on May 21 (UT) 17:22:33. We took several unfiltered frames with 60 s exposure. In the enhanced XRT error circle (Beardmore et al., GCN 21107) we do not detect the afterglow. Preliminary photometry of the afterglow is following: Date UT start t-T0 Filter Exp. OT Err. UL Telescope (mid, days) (s) (3 sigma) 2017-05-20 18:42:38 1.58414 R 24*120 20.06 0.06 21.4 Zeiss-1000 2017-05-21 15:58:25 2.48340 R 39*120 20.95 0.14 21.6 Zeiss-1000 2017-05-22 15:27:05 3.46168 R 39*120 22.20 0.40 21.9 Zeiss-1000 2017-05-21 17:22:33 2.52050 CR 20*60 n/d n/d 20.8 AS-32 The photometry is based on nearby SDSS stars, reported by Mazaeva et al. (GCN 21169). The light curve of the GRB 170519A afterglow based on our observations (GCNs 21162, 21169, 21206) can be found at http://grb.rssi.ru/GRB170519A/GRB170519A_lc.png