[vsnet-grb-info 19297] GRB 170405A: ISON/Terskol optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  20992
SUBJECT: GRB 170405A: ISON/Terskol optical observations
DATE:    17/04/06 12:12:17 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

E. Mazaeva (IKI),  V. Agletdinov (KIAM),  A. Pozanenko (IKI), A. Volnova 
(IKI),   I. Molotov (KIAM)  report on behalf of  larger GRB follow-up 
collaboration:

We observed the field of GRB 170405A (Troja et al., GCN 20984) with 
K-800 (0.8m) telescope  of ISON/Terskol   observatory starting  on 
April, 05 (UT) 19:12:55, i.e. 45 minutes after GRB onset.  We obtained 
several unfiltered images of 15 s exposure. The optical afterglow Troja 
et al., GCN 20984; Malesani et al., GCN 20988; Klotz et al., GCN 20989; 
Ugarte Postigo et al., GCN 20990;    Martin-Carrillo et al., GCN 20991) 
is clearly visible in combined images. Preliminary photometry   of the 
afterglow is following


Date       UT start   t-T0    Filter  Exp.   OT     Err.  UL
                       (mid, days)     (s)

2017-04-05 19:12:55 0.03139 CR 72*15  17.27 0.10 20.1
2017-04-05 19:34:33 0.04300 CR 48*15  17.96 0.13 19.8
2017-04-05 19:49:05 0.06019 CR 110*15 18.39 0.14 20.4
2017-04-05 20:23:55 0.08543 CR 110*15 19.18 0.22 20.2
2017-04-05 21:01:48 0.11099 CR 107*15  n/d n/d   18.9

Photometry is based on nearby USNO-B1.0 stars
USNO-B.1_id     R2
0647-0315771    15.13
0647-0315754    15.45
0647-0315872    15.34
0647-0315921    15.08
0647-0315788    14.92

Preliminary light curve of the afterglow can be found in
http://grb.rssi.ru/GRB170405A/GRB170405A_light_curve.png