TITLE: GCN CIRCULAR NUMBER: 23113 SUBJECT: GRB180809B: MASTER Triple Independent Automatic OT Detection DATE: 18/08/10 09:07:16 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs N.Tiurina, V. Lipunov, E. Gorbovskoy, V.Kornilov, A.Kuznetsov, V.Chazov, I. Gorbunov, D.Zimnukhov, D.Kuvshinov, P.Balanutsa, V.Vladimirov, D. Vlasenko Lomonosov Moscow State University,SAI R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias (IAC) D. Buckley, South African Astronomical Observatory (SAAO) 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) We have already reported the observation of the optical transient GRB 180809B (Moss et al., GCN # 23105) by one of the telescopes of the MASTER Global Network (Lipunov et al., GCN 23109). Here we report on the triple independent, automatic detection of the optical transient (also found by Swift UVOT (Moss et al., GCN 23105)). The relatively later guidance of the three MASTER robotic telescopes is due to the fact that the first socket message did not indicate the time of the trigger. As a result, everyone went to the CALET Alert (trig number 1217881726) with poor defined coordinates. Nevertheless, we were able to obtain detailed light curves with a maximum in 4 polarizations. MASTER-SAAO robotic telescope (MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the GRB180809.85 16 sec after notice time and 111 sec after trigger time at 2018-08-09 20:30:39 UT. On our 1-th (10s exposure) set in two polarizations (/\), obtained 111 sec after tigger time at 2018-08-09 20:30:39 UT, we found 1 optical transient within SWIFT error-box (ra=299.7 dec=-15.2989 r=0.05) brighter then 17.4. T-Tmid Date Time Expt. Ra Dec Mag s UT s -------|--------------------|-------|-----------------|---------------|------- 116 2018-08-09 20:30:39 10 (19h 58m 48.0s , -15d 17m 57.1s) 16.5 The 5-sigma upper limit has been about 17.9 mag The observations started on zenit distance = 21 deg., galactic latitude b = -22 deg. The moon ( 4 % bright part) was below the horizon (The altitude of the Moon = -75 deg ). The sun altitude = -56.3 degree. The object can be observed till 2018-08-10 04:03:58 UT. MASTER-Tavrida robotic telescope (MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the GRB180809.85 35 sec after notice time and 133 sec after trigger time at 2018-08-09 20:31:01 UT. On our first (10s exposure) set we found 1 optical transient within SWIFT error-box (ra=299.7 dec=-15.2989 r=0.05) brighter then 17.9: T-Tmid Date Time Expt. Ra Dec Mag s UT s ------|--------------------|-------|-----------------|-----------------|------- 138 2018-08-09 20:31:01 10 ( 19h 58m 48.0s , -15d 17m 56.5s) 16.8 The 5-sigma upper limit has been about 17.9 mag The observations made on zenit distance = 60 degrees, galaxy latitude b = -22 degree. The moon ( 4 % bright part) below the horizon (The altitude of the Moon is -25 degree ). The sun altitude is -27.0 degree. The object can be observed till 2018-08-10 01:29:20. MASTER-IAC robotic telescope (MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Spain (IAC Teide Observatory) was pointed to the GRB180809.85 120 sec after notice time and 147 sec after trigger time at 2018-08-09 20:31:15 UT in two polarizations (|-). On our first set, obtained we found 1 optical transient within SWIFT error-box (ra=299.7 dec=-15.2989 r=0.05): T-Tmid Date Time Expt. Ra Dec Mag ---------|---------------------|-------|-----------------|-----------------|------- 152 2018-08-10 20 31 15 20 ( 19h 58m 43.3s , -15d 20m 37.9s) 15.5 The 5-sigma upper limit has been about 16.0 magThe message may be cited. The observations made on zenit distance = 44 degrees, galaxy latitude b = -22 degree. The moon ( 3 % bright part) below the horizon (The altitude of the Moon is -41 degree ). The sun altitude is -9.1 deg. The object can be observed till 2018-08-10 05:19:05 UT. The message may be cited.