TITLE: GCN CIRCULAR NUMBER: 19116 SUBJECT: GRB 160227A: MASTER prompt OT Detection and LC DATE: 16/02/29 17:15:15 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V.Krushinski, I.Zalozhnich, A. Popov Ural State University, Kourovka E. Gorbovskoy, V. Lipunov, N.Tyurina, V.Kornilov, P.Balanutsa, A.Kuznetsov, D.Kuvshinov Lomonosov Moscow State University, Sternberg Astronomical Institute, Moscow State University A.Gabovich, V.Yurkov, Yu.Sergienko, D.Varda Blagoveschensk Educational State University, Blagoveschensk K.Ivanov, N.M.Budnev, O.Gres, V.A.Poleshchuk Irkutsk State University A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory R. Rebolo, M. Serra-Ricart, N. Lodieu, G. Israelian The Instituto de Astrofisica de Canarias Five telescopes of MASTER Net of robotic telescope participated in the observation of the GRB 160227A. Two telescopes detected prompt optical emission. We discovery very strong OT variations with time ~100 sec correlated with gamma ray flux (Sakamoto et al., 19106). MASTER-Ural robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Ural was pointed to the GRB160227A 30 sec after notice time and 115 sec after trigger time at 2016-02-27 19:34:03 UT. On our first (20s exposure) set we found 1 optical transient within SWIFT error-box (Siegel et al GCN 19098; Gorbovskoy et al GCN 19099) at a position: RA 12h 59m 14.13s Dec +78d 40m 44.2s With magnitude automatical magnitude ~ 17.3 We definetly see OT at a number of single and coadd images. OT was observed during ~ 1 hours. We see OT decay from 17.0 to 19.1 mag in the time interval from 115 to 2647 sec atger the trigger. The 5-sigma upper limit has been about 17.5 mag on first single image and up to 19.5 mag at on coadd images in later time. MASTER-Kislovodsk robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Kislovodsk was pointed to the GRB160227A (Siegel et al GCN 19098) 52 sec after notice time and 137 sec after trigger time at 2016-02-27 19:34:25 UT. On our first (30s exposure) set we marginaly see optical transient (Siegel et al GCN 19098, Gorbovskoy et al GCN 19099) within SWIFT error-box. OT also definetly seen at a number of coadd images. OT was observed for about 4 hours. We see OT decay from 18.1 to ~ 20.5 mag in the time interval from 152 to 12900 sec atger the trigger. The 5-sigma upper limit has been about 17.5 mag on first single image and up to 21.0 mag at on coadd images in later time. MASTER-IAC robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in IAC was pointed to the GRB160227A 49 sec after notice time and 137 sec after trigger time at 2016-02-27 19:34:25 UT. On our first (30s exposure) set we haven`t found optical transient within SWIFT error-box. The observations started on evening sky (Sun altitude ~ -6 deg). Therefore, the first exposure upper limit is very low. We definetly see OT at a number of coadd images, starting ~ 1 hour after the trigger. OT was observed for about 2 hours. We see OT decay from 19.0 to 20.0 mag in the time interval from 3400 to 9200 sec atger the trigger. The 5-sigma upper limit has been about 14.5 mag (due to bright evening sky ) on first single image and up to 21.0 mag at on coadd images in later time. MASTER-Tunka robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Astrophysical Center Tunka was pointed to the GRB160227A 17 sec after notice time and 103 sec after trigger time at 2016-02-27 19:33:51 UT. On our first (20s exposure) set we haven`t found optical transient within SWIFT error-box. The observations made on not very well weather condition and was finished 10 after GRB, due to snow coming. The 5-sigma upper limit has been about 15.3 mag on first single image. MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Blagoveschensk was pointed to the GRB160227A 8 sec after notice time and 93 sec after trigger time at 2016-02-27 19:33:41 UT. On our first (20s exposure) set we haven`t found optical transient within SWIFT error-box. The 5-sigma upper limit has been about 16.0 mag on first single image. Out preliminary photometry results available at table 1 Light curve available here: http://master.sai.msu.ru/static/grb160227.png Table 1. T0-Tmig Expt. Mag Site Coadd -------|-------|------|---------------------|------ 125 20 17.0 MASTER Ural 152 30 18.1 MASTER Kislovodsk 174 30 18.5 MASTER Ural 207 120 17.8 MASTER Kislovodsk 3 231 40 17.7 MASTER Ural 299 50 18.9 MASTER Ural 383 70 19.6 MASTER Ural 485 90 17.9 MASTER Ural 607 110 18.0 MASTER Ural 621 550 18.7 MASTER Kislovodsk 4 757 140 18.7 MASTER Ural 935 170 18.2 MASTER Ural 1133 180 19.1 MASTER Ural 1349 180 19.0 MASTER Ural 1566 180 18.9 MASTER Ural 1765 1080 18.9 MASTER Kislovodsk 6 1781 180 19.1 MASTER Ural 1998 180 19.1 MASTER Ural 2647 900 19.1 MASTER Ural 5 2789 360 19.7 MASTER Kislovodsk 2 3423 540 19.0 MASTER IAC 3 4261 900 19.2 MASTER IAC 5 4527 900 19.4 MASTER Kislovodsk 5 5966 1080 19.5 MASTER Kislovodsk 6 6401 1800 20.0 MASTER IAC 10 7771 3600 19.9 MASTER IAC 20 9196 1800 19.8 MASTER IAC 10 10608 1620 20.9 MASTER Kislovodsk 9 12824 1800 20.3 MASTER Kislovodsk 10 The message may be cited.