[vsnet-grb-info 15517] GRB 140907A: MASTER optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16806
SUBJECT: GRB 140907A: MASTER optical observations
DATE:    14/09/09 13:03:53 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <gcncirc at observ.inetcomm.ru>

E. Gorbovskoy, V. Lipunov, M.Pruzhinskaya, V.Kornilov, D.Kuvshinov, 
N.Tyurina, N.Shatskiy, P.Balanutsa, D.Zimnukhov, A.Kuznetsov, V.V.Chazov, 
D.Denisenko,  A.Sankovich
Lomonosov Moscow State University,
Sternberg Astronomical Institute, Moscow State University

V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov, A. Gabovich
Blagoveschensk Educational State University, Blagoveschensk

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

V.Krushinski, I.Zalozhnih,  A. Popov
Ural Federal University, Kourovka

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

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

Claudio Mallamaci, Carlos Lopez and Federico Podest
Observatorio Astronomico Felix Aguilar (OAFA)

MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in Blagoveschensk was pointed to the  GRB140907A 6987 sec after 
notice time and 7504 sec after trigger time at 2014-09-07 18:12:13 UT 
directly after weather conditions became suitable. On our first (180s 
exposure)  set we found optical transient  within Swift error-box (ra=03 
12 34 dec=+46 36 18 r=0.050000) on coadditional images in two epoch.
The protometry results available at Table 1.


Table 1.

Date and  Time start  T_trig-Tmid  Exptime    Mag   err.mag

2014-09-07 18:12:13.4   7809        540      19.0     0.2
2014-09-07 19:23:43.6  12547       1260      19.4     0.2

The  approximate power law index (alpha) from 7000 to 13000 seconds after 
the trigger is  about 0.81 +- 0.1  (F ~ t^-alpha).

Another two MASTER-II robotic telescop located in Kislovodsk and Tunka 
made upper limit observations only in earlier time due to weather 
conditions and high zenith distance of object.  MASTER II  in Tunka was 
pointed to the  GRB140907A  1021 sec after trigger time at 2014-09-07 
16:24:10 directly after weather conditions became suitable. On our first 
(180s exposure) image we haven`t found optical transient up to 16m. MASTER 
II in Kislovodsk starting observations  GRB140907A 17 sec after notice 
time and 77 sec after trigger time at 2014-09-07 16:08:25 using FERMI GBM 
coordinates. However OT position was not covered by MASTER-II. The 
telescope pointing by Swift trigger 22 sec after notice time and 540 after 
trigger time at 2014-09-07 16:16:08.  On first (110s exposure) image we 
haven`t found optical transient up to 12.5 m. The zenith distance of 
object z~85 d.

Our white (clear) band is well described by a parity 0.8R+0.2B (USNO B1).