TITLE: GCN CIRCULAR NUMBER: 20650 SUBJECT: Fermi Trigger 508295323: MASTER-OAFA possible OT detection DATE: 17/02/09 20:28:51 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs R.Podesta, C.Lopez, F. Podesta Observatorio Astronomico Felix Aguilar (OAFA) , National University of San Juan, Argentina H. Levato, C. Saffe Instituto de Ciencias Astronomicas,de la Tierra y del Espacio (ICATE), San Juan, Argentina V. Lipunov, E. Gorbovskoy, V.Kornilov, D.Kuvshinov, N.Tyurina, A.V.Krylov, I.Gorbunov, P.Balanutsa, A.Kuznetsov, V.V.Chazov Lomonosov Moscow State University, Sternberg Astronomical Institut of MSU K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov Blagoveschensk Educational State University, Blagoveschensk A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Senik Kislovodsk Solar Station of the Pulkovo Observatory D.Buckley, S. Potter, A.Kniazev, M.Kotze South African Astronomical Observatory R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias MASTER-OAFA robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in OAFA was starting inspection of the FERMI trigger 508295323 (GRB170209.05) error-box (ra=07h 33m 36s dec=-49d 38' 23" r=3.22 https://gcn.gsfc.nasa.gov/other/508295323.fermi GRB_TIME: 2017-02-09 01:08:38.08UT) 112 sec after trigger time at 2017-02-09 01:10:30 UT. The 5-sigma upper limit on our 60s exposure set is 18.6 mag . MASTER OT J072307.30-521446.6 discovery - possible optical counterpart of Fermi During Fermi 508295323 trigger ( https://gcn.gsfc.nasa.gov/other/508295323.fermi GRB_TIME: 2017-02-09 01:08:38.08UT) inspection MASTER-OAFA auto-detection system discovered new OT source at (RA, Dec) = 07h 23m 07.30s -52d 14m 46.6s on 2017-02-09 02:07:07.478UT with unfiltered m_OT=17.4 (mlimit=18.1m). The second image is on 02:14:07.83 UT with m_OT=17.4. There are only 2 inspection images of this area, the GRB_ERROR was 3.22 deg radius, and we cover full field in inspection mode by 2 images. There is no minor planet at this place. There is no any sources in VIZIER database, it means 22mag upper limit in POSS (Palomar) images. We have reference image without OT on 2017-01-29.17249 UT with 19.6 unfiltered magnitude limit. MASTER-SAAO reobserved it on 2017-02-09 18:37:14UT (sunset in SAAO, Sun altitude is -12.0). There is no OT brighter 18.7m. Deep photometry and spectral observations are required. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/072307.30-521446.6.png The detection made on zenit distance = 76 degrees, galaxy latitude b = -83 degree. The sun altitude was -24 degree. The moon ( 0 % bright part) was below the horizon (the altitude of the Moon is -14 degree ). The message may be cited.