GCN Circular 19651

I. Bikmaev, E. Irtuganov, N. Sakhibullin (KFU/AST),
R. Burenin, M. Pavlinsky, R. Sunyaev (IKI),
I. Khamitov, H. Kirbiyik (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.)

report:

We observed field of Fermi GRB 160625B (Dirirsa et al. GCN 19580
Not found
 
 
) at
the position of optical afterglow (Troja et al. ,GCN 19588) with
Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK National
Observatory, Turkey) using the TFOSC instrument.

We obtained series of Rc exposures in June 30 / July 01(6 frames x 600
sec, UT = 00:21 - 01:30 ), in July 01 / 02 (4 frames x 900 sec, UT =
00:36 - 01:42), in July 02 / 03 (6 frames x 900 sec, UT = 23:49 -
01:29), and in July 03 / 04, 2016, (14 frames x 600 sec, UT = 22:50 -
01:39). The optical transient (Troja et al. GCN 19588
Not found
 
 
; Oates et
al. GCN 19589
Not found
 
 
; Kuroda et al. GCN 19599
Not found
 
 
; Xu et al. GCN 19600
Not found
 
 
; D'Elia et
al. GCN 19601
Not found
 
 
; Watson at al. GCN 19602
Not found
 
 
; Karpov et al. GCN 19603
Not found
 
 
;
Mazaeva et al. GCN 19605
Not found
 
 
, 19620
Not found
 
 
; Moskvitin et al. GCN 19611
Not found
 
 
;
Gorbovskoy et al. GCN 19612
Not found
 
 
; Batsch et al.  GCN 19615
Not found
 
 
; Cobb et al. GCN
19616
Not found
 
 
; Guidorzi et al. GCN 19640
Not found
 
 
; Valeev et al. GCN 19642
Not found
 
 
) is clearly
detected in each images.

Using USNO-B1 0969-0608410 star at RA,DEC = 308.580912 +06.909881
(J2000.0) with R = 16.73 mag as a reference we estimated the
Rc-magnitudes of the afterglow in stacked images:

 T-T0,  Mag., Mag.err
 days

 5.09   20.69 +- 0.03  
 6.10   20.96 +- 0.04  
 7.08   21.04 +- 0.03  
 8.06   21.24 +- 0.04  

RTT-150 data show that OT is fading at approximately the same power
law rate as it was observed earlier.