GCN Circular 21091

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, D.Kuvshinov, A.V.Krylov, 
I.Gorbunov, P.Balanutsa, A.Kuznetsov, V.V.Chazov, D. Vlasenko
Lomonosov Moscow State University, Sternberg Astronomical Institut

D.Buckley, S. Potter, A.Kniazev, M.Kotze
South African Astronomical Observatory

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


K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk, O. Ershova 
Irkutsk State University

V.Yurkov, Yu.Sergienko
Blagoveschensk Educational State University, Blagoveschensk

A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov
Kislovodsk Solar Station of the Pulkovo Observatory

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias


MASTER-SAAO  robotic telescope (MASTER-Net: http://observ.pereplet.ru) located 
in SAAO was starting survey on the LAT  GRB170510.22 error-box (Bissaldi et 
al., GCN #21080)   22480 sec after notice time and 41530 sec after trigger time 
at 2017-05-10 16:44:36 UT. The 5-sigma upper limit on our first (180s exposure) 
set is about 18.9 mag

  We marginaly see   optical candidate (Cucchiara  et al. GCN 21087
Not found
 
 
) at XRT 
(Evans  et al. GCN #21082, Melandri et al. GCN #21086)  position with 
unfiltered mag ~ 19  m .

Ra, Dec = 10 40 36.76 -39 12 43.8 (+/-1 arcsec)

We did not see object 2.5 hours late with limit 19.5 .

So X-ray Source 1 (Melandri et al. GCN #21086) is possible OT.

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