[vsnet-grb-info 21748] GRB 190203A: SAO RAS optical observations, afterglow fading

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23847
SUBJECT: GRB 190203A: SAO RAS optical observations, afterglow fading
DATE:    19/02/03 18:43:44 GMT
FROM:    Moskvitin Alexander at SAO RAS  <mosk at sao.ru>

A. S. Moskvitin and O. I. Spiridonova (SAO RAS),
A. A. Volnova (IKI RAS), report on behalf of larger collaboration.


We observed the field of the GRB 190203A (Lien et al. GCNC #23845)
with the Zeiss-1000 telescope of SAO RAS (+ CCD photometer),
started on February, 3, 15:54:38 UT (10.5 min after the trigger).

We clearly detected the OT in the first few 300 sec. Rc band frames
(coordinates are consistent with the reported UVOT position).

Preliminary measurements of the OT brightness are as following:

T_start, UT  T_end     T_mid-T0, h   exp., s      R     +/- R_err
15:54:38     16:11:51  0.318         3 x 300      19.34 +/- 0.08
16:12:54     16:30:11  0.624         3 x 300      20.46 +/- 0.12
16:30:54     17:19:23  1.183         8 x 300      21.23 +/- 0.14

OT is fading quickly with the slope about -1.3.
The photometry is based on the nearby USNO-B1 stars.
No correction has been made for the Galactic extinction.