[vsnet-grb-info 20967] GRB 180728B: MASTER optical observations short GRB IPN error box

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23065
SUBJECT: GRB 180728B: MASTER optical observations short GRB IPN error box 
DATE:    18/07/31 06:56:36 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov at xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, P.Balanutsa, N.Tiurina, D.Vlasenko, V.Kornilov, 
A.Kuznetsov,  V.Chazov, I.  Gorbunov, D.Zimnukhov, D.Kuvshinov, 
V.Vladimirov,
Lomonosov Moscow State University,SAI

D.Svinkin (Ioffe Institute, StPetersburg, Russia)

D. Buckley,
South African Astronomical Observatory (SAAO)

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

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

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

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

O. Gres, N.M.Budnev , Yu.Ishmuhametova
Irkutsk State University (ISU)

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

MASTER-SAAO  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in SAAO was starting survey on the IPN  GRB180728B error-box 
(Svinkin et al., GCN Circ #23056; Hamburg et al., GCN Circ #23057)  14269 
sec after notice time and 70698 
sec after trigger time at 2018-07-29 16:48:15 UT. The 5-sigma upper limit 
on our first (180s exposure)  set is about 18mag.

The typical limit of coadded images is about 20 mag.
We marginally found one candidate to uncataloged object source near 
PGC052927 galaxy:

MASTER OT J144922.8+164418.2

RA,DEC = 14h 49m 22.8s +16d 44' 18.2"    error = 0.7 arcsec
mag = 19.7;
The offset from galaxy is 10.8W	and 22.2N arcsec.

====================================================================

The observations made on zenit distance = 50 degrees, galactic latitude b 
=  61 degree.
The moon (97 % bright part) below the horizon (The altitude of the Moon is 
-8 deg.
Observations started at twilight.
The sun  altitude  is -11.1 deg.
The object can be observed till sunrise at 2018-07-30 05:26:48.


The covered map is available at
http://master.sai.msu.ru/static//IPN/db/GRB180728.88/img/ligo_master_2018-07-30-16-09-11.eb.zoom.1.png


We reobserved possible transient on the next night starting 2018-07-30
16:57:46 UT. We do not find the
object brighter than  20.5 .