TITLE: GCN CIRCULAR NUMBER: 18738 SUBJECT: LIGO/Virgo G211117: MASTER Observations and Inspection + OT DATE: 15/12/28 19:05:25 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, N.Tyurina, V.Kornilov, P.Balanutsa, A.Kuznetsov Lomonosov Moscow State University, Sternberg Astronomical Institute D.Buckley, S. Potter, M. Kotze South African Astronomical Observatory R. Rebolo, M. Serra-Ricart, G. Israelian, N.Lodiu The Instituto de Astrofisica de Canarias A. Tlatov, V.Sennik Kislovodsk Solar Station of the Pulkovo Observatory O. Gress, K. Ivanov, N.M. Budnev Irkutsk State University V.Yurkov, Yu.Sergienko, A.Gabovich Blagoveschensk Educational State University, Blagoveschensk MASTER-IAC robotic telescope (MASTER-Net: http://observ.pereplet.ru, 2x4 square degrees) located in IAC was pointed to the LIGO/Virgo G211117 event (Possible Gravitational Wave Burst) 7975 sec after notice time and 1 days 58376 sec after trigger time at 2015-12-27 19:51:49 UT. Our first (180s exposure) set we have 5-sigma upper limit has been about 20.0 mag (unfiltered). MASTER-SAAO robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in SAAO was pointed to the LIGO/Virgo G211117 event 19726 sec after notice time and 1 days 70127 sec after trigger time at 2015-12-27 23:07:40 UT. On our first (180s exposure) set we haven`t found optical transient within LIGO error-box (ra=02 31 59 dec=+07 59 59 r=0.100000). The 5-sigma upper limit has been about 20.2mag (unfiltered). The message may be cited. MASTER-Kislovodsk robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in SAAO was pointed to the LIGO/Virgo G211117 event 9608 sec after notice time and 1 days 60009 sec after trigger time at 2015-12-27 20:19:02 UT. On our first (180s exposure) set we have 5-sigma upper about 15.3mag (unfiltered). The full Coverage map starting after trigger (47.5 % total probability - north + south segment) is available here: http://master.sai.msu.ru/static/G211117_MASTER_NET.png This map includes both independently MASTER survey of the alert area on 26th after , and Inspect images after the notice time (2015-12-27 17:38) Four MASTER VWF (very wide field FOV = 2 x 386 sq. degree, d=82 mm f/1.2) cameras at Kislovodsk and Canary Island cover 4.3 % of total probability field synchronously with Ligo trigger at 2015-12-26 03:38:53 UTC. I.e we have a set of 5 seconds images before, during and after trigger without time gaps. The 3 sigma upper limit is about 11 mag at a single (5 seconds) image and 12 mag at a coadd of 12 images with total exposure 60 sec. Coverage map available here: http://master.sai.msu.ru/static/G211117_WF.png We detected second OT during inspection. MASTER OT J124246.31+111448.6 - possible QSO in active state not relaited with gravitational wave event. MASTER-IAC auto-detection system discovered OT source at (RA, Dec) = 12h 42m 46.31s +11d 14m 48.6s on 2015-12-28.28271 UT (error box 1 arcsec). The OT unfiltered magnitude is 18.9m (limit 19.5m). The OT is seen in 3 images. There is no minor planet at this place. We have reference image without OT on 2015-12-28.25404 UT with unfiltered magnitude limit 20.0 m. There is possible QSO SDSS 124246.25+111449.0 inside our error box. We have long story of the avout 2 magnitude variability this sources in Tunka nad Kislovodsk MASTERs DataBase. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/124246.31111448.6.png The reduction is continuated. This circular is an official product of the MASTER team.