GCN Circular 20650

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.