TITLE:   GCN CIRCULAR
NUMBER:  23851
SUBJECT: Swift Trigger 887541: MASTER optical observation
DATE:    19/02/04 00:39:41 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, N.Tyurina, V.Kornilov, D.Vlasenko, V.Vladimirov, 
D.Zimnukhov, A.Kuznetsov, P.Balanutsa, A. Chasovnikov, D.Kuvshinov (Lomonosov 
Moscow State University, SAI, Physics Department),

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

D. Buckley (South African Astronomical Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko, D. Kobcev (Blagoveschensk Educational 
State University),

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

O. Gress, N.M. Budnev, O.Ershova, Yu.Ishmuhametova (Applied Physics Institute, 
Irkutsk State University),

R. Podesta, C. Lopez, C.Francile, F. Podesta (Observatorio Astronomico Felix 
Aguilar OAFA),

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

MASTER-SAAO robotic telescope (Global MASTER-Net http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, v.2010, 30L)
was pointed to Swift Trigger 887541  (Barthelmy  et al. GCN23849,Ttrig=2019-02-03 21:18:17UT)
~3h after trigger time (at alert time error-box was under the horizon at all MASTER observatories)
at  2019-02-04 00:16:44UT.

There is no OT inside Swift-XRT error-box with unfiltered mlim=17.5 
(5sigma, 180s exposition)

The observations started when error-box altitude was 9 deg.
The sun altitude was -38deg.
The message may be cited.