[vsnet-grb-info 19944] GRB 171020A: Confirmation of OT fading

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22031
SUBJECT: GRB 171020A: Confirmation of OT fading
DATE:    17/10/21 03:32:12 GMT
FROM:    Moskvitin Alexander at SAO RAS  <mosk at sao.ru>

A. Moskvitin (SAO RAS), O. Spiridonova (SAO RAS), A. Volnova (IKI RAS)

We observed the field of GRB 171020A (Page et al., GCN 22028)
with the 1-m telescope of SAO RAS, Zeiss-1000 on 2017.10.20,
starting at 23:18 UT, i.e. ~11 minutes after the trigger.
The OT (Malesani et al., GCN 22029) is clearly detected
in the individual 300 sec. frames. The coordinates of OT:
R. A. = 02:36:59.62; Dec. = +15:12:15.6 (J2000).


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

2017.10.20 23:18:05  0.02016      Rc     6*300 20.9 +/- 0.1   22.3
           23:55:27  0.04827      Rc     7*300 21.5 +/- 0.1   22.5



The temporal decay slope is about -0.3, F ~ (t-T0)^alpha.

The calibration were made against the nearby USNO-B1.0 stars
(R2 magnitudes):
1051-0026883 02:37:00.38 +15:11:09.6 18.59
1052-0027787 02:36:57.49 +15:12:36.8 16.62
1052-0027776 02:36:50.26 +15:12:39.8 18.15