[vsnet-grb-info 18528] GRB 161001A: MASTER-OAFA and MASTER-SAAO early optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19976
SUBJECT: GRB 161001A: MASTER-OAFA and MASTER-SAAO early optical observations
DATE:    16/10/02 10:08:33 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov at xray.sai.msu.ru>

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

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

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

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

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

K.Ivanov, J.Rabinovich, N.M.Budnev,
Irkutsk State University

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

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

MASTER-OAFA  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in OAFA was pointed to the  GRB161001A 29 sec after notice 
time and 41 sec after trigger time at 2016-10-01 01:05:57UT. On our 
first (10s exposure)  set we  not found OT within 6 square degrees 
field around  SWIFT BAT  error-box (Page et al., GCN 19967; Markwardt et 
al.,GCN 19974 ) brighter then 16.7  unfiltered magnitude.

MASTER-SAAO  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in SAAO was pointed to the  GRB161001A 167 sec after notice time 
and 176 sec after trigger time at 2016-10-01 01:08:17 UT. On our first 
(40s exposure)  set we haven`t found optical transient  within SWIFT 
error-box.

The 5-sigma upper limit has been about 18.4 mag

We found optical object at first hour coadded images  by both MASTERs 
telescopes at coordinates Ra 04:47:40.83 Dec -57:15:38.07 (+-0.7 arcsec 
error) with unfiltered magnitude:

0.8R +0.2B = 20.6 (+0.1 -0.4)

with respect to USNO B stars. We  have archival images in MASTER SAAO 
DataBase at 2016-04-09  with 20.9 3-SIGMA limit. We see same object at 
same position.

We note that our scale is 1 pix ~ 2 arcsec . So the DSS2 object  (Kruehler 
et al., GCN 19971)  and GROND afterglow candidate (Chen et al., GCN 19975) 
are inside the our pixel.

The message may be cited.