[vsnet-grb-info 23948] Swift GRB191020.81: Global MASTER-Net OT detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  26047
SUBJECT: Swift GRB191020.81: Global MASTER-Net OT detection
DATE:    19/10/20 19:47:21 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov at xray.sai.msu.ru>

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

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

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

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

R. Podesta, Carlos Lopez and F. Podesta
Observatorio Astronomico Felix Aguilar (OAFA)

Hugo Levato
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

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

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

MASTER-Tavrida robotic telescope (Global 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  GRB191020.81 20 sec after notice time and 297 sec after trigger time at 2019-10-20 19:25:00 UT. On our 6-th (180s exposure)  set , obtained 925 sec after tigger time at 2019-10-20 19:35:29 UT, we  found 1 optical transient within Swift error-box (ra=339.992 dec=-17.3211 r=0.1) brighter than 18.55.


 T-Tmid      Date      Time       Expt.        Ra                Dec           Mag
---------|---------------------|-------|-----------------|-----------------|-------
    1015   2019-10-20 19:35:29     180   (22h 39m 57.886s , -17d 24m 35.54s)    15.97

The OT has irregular early time  behaviour since 1139 till 1532.5 seconds after the trigger.
The 5-sigma upper limit has been about 18.55mag
The message may be cited.