TITLE: GCN CIRCULAR NUMBER: 23361 SUBJECT: Baksan Neutrino BNO 181021: Global MASTER-net Optical Follow-up Observations DATE: 18/10/22 11:44:31 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V.Lipunov, E. Gorbovskoy, N.Tiurina, V.Kornilov, A.Kuznetsov, D.Zimnukhov, D.Kuvshinov, P.Balanutsa, V.Vladimirov, D.Vlasenko Lomonosov Moscow State University,SAI V.B. Petkov, M.M. Boliev, A.N. Kurenya, Baksan Neutrino Observatory, Institute for Nuclear Research of RAS, Moscow, Russia N.M.Budnev, O. Gres, Yu.Ishmuhametova Irkutsk State University (ISU) D. Buckley, South African Astronomical Observatory (SAAO) R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias (IAC) A. Tlatov, V.Senik, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory R. Podesta, F. Podesta, C. Lopez, C.Francile Observatorio Astronomico Felix Aguilar (OAFA) H.Levato, Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) O. Gres, N.M.Budnev , Yu.Ishmuhametova Irkutsk State University (ISU) A. Gabovich, V. Yurkov, Yu. Sergienko Blagoveschensk Educational State University (BSPU) Global MASTER Robotic Net started new follow up optical observations of high energy (> 1Gev) neutrino from Baksan Neutrino Observatory Alerts (Petkov et al., Physics of Particles and Nuclei, 2015,Vol. 46, pp. 201-204.). MASTER-Tunka robotic telescope (MASTER-Net: Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L http://observ.pereplet.ru) located near Baykal Lake (Russia) started Baksan Neutrino Observatory BNO181021.79 ( RA_2000=124.3,+08.3, error-box=03deg, TriggerTime=2018-10-21 19:09:43UT, NoticeTime=19:50:20.18 UT) alert observations at 2018-10-21 19:50:49 UT (20 sec after notice time, 2466 sec after trigger time). The 5-sigma upper limit on our 540s images is 19.2 mag. Observations started, when Object_Altitude: 28.56 deg Sun_Altitude: -35.34 deg Moon_Altitude: 4.43 deg, Dist. to Moon: 128.694199 deg, Lunar disk: 0.91 Gal. latitude: 23.34deg, Gal. longitude: 215.67deg MASTER-Tavrida robotic telescope, located in Lomonosov MSU, SAI Crimea astronomical station, started BNO181021.79 alert inspection at 2018-10-21 23:54:02UT (17059 sec after trigger time) and observed till 2018-10-22 00:21:59UT. The 5-sigma upper limit on our 540s images is 19.0. Observations started, when Object_Altitude: 25.90 deg Sun_Altitude: -43.89 deg Moon_Altitude:13.64 deg, Dist. to Moon: 126.65 deg, Lunar disk: 0.92 Gal. latitude: 23.34deg, Gal. longitude: 215.67deg MASTER-SAAO robotic telescope, located in South African Astronomical Observatory, started BNO181021.79 alert inspection at 2018-10-22 01:50:11UT (20528 sec after trigger time). and observed it till 2018-10-22 03:00:55UT . The 5-sigma upper limit on our 540s images is 20.0. Observations started, when Object_Altitude: 30.8 deg Sun_Altitude: -23.59 deg Moon_Altitude: 10.92 deg, Dist. to Moon: 125.65 deg, Lunar disk: 0.92 Gal. latitude: 23.34deg, Gal. longitude: 215.67deg There are two QSOs inside neutrino error box. First of them has RA,DEC = 08 10 26.42 +10 10 40.99 in 0.421" with z=2.50589 (unfiltered MASTER magnitude m = 17.2 ). But there is no significant variability of its brightness since 2011-11-26 20:43:35.857UT in MASTER-Tunka database. Second one has coordinates 08 15 29.47 +09 54 40.7 with Z=1.7 and rmag=20.04 . The message may be cited.