GCN Circular 20392

V.M.  Lipunov, O.Gress, N.Tyurina, E. Gorbovskoy, V.G. Kornilov, 
P.Balanutsa, 
A.Kuznetsov, V.Shumkov, M.I.Panchenko Lomonosov Moscow State University, 
Sternberg Astronomical Institute

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

R. Rebolo, M. Serra-Ricart, G. Israelian, N.Lodiu
The Instituto de Astrofisica de Canarias

A. Tlatov, V.Sennik
Kislovodsk Solar Station of the Pulkovo Observatory

N.M. Budnev, O. Gress, K. Ivanov
Irkutsk State University

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


MASTER OT J105811.78+811432.6 discovery - BLA flare in GW170401 field

MASTER-Kislovodsk auto-detection system discovered OT source at (RA, Dec) 
= 10h 58m 11.78s +81d 14m 32.6s on 2017-01-06.74507 UT.

The OT unfiltered magnitude is 16.1m (limit 19.4m).

The OT is seen in 11 images. There is no minor planet at this place.

We have reference image without OT on 2012-10-20.65339 UT with unfiltered 
magnitude limit 19.7m.

There is Blazar with gamma-ray counterpart in 0.57" ( 
http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=&-out.add=_r&-out.add=_RAJ%2C_DEJ&-sort=_r&-to=&-out.max=20&-meta.ucd=2&-meta.foot=1&-c=164.5490875+81.242377777778&-c.rs=5 
)

Spectral observations are required.

The discovery and reference images are available at:

http://master.sai.msu.ru/static/OT/MASTEROTJ105811.78+811432.jpg