TITLE:   GCN CIRCULAR
NUMBER:  27318
SUBJECT: GRB 200228B: continued optical observations
DATE:    20/03/05 18:07:39 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

A. Pozanenko (IKI), S. Belkin (IKI), R. Ya. Inasaridze (AbAO),  E. 
Klunko (ISTP), A. Kusakin (FAPHI),  I. Reva (FAPHI), V. Rumyantsev 
(CrAO), E. Mazaeva (IKI), A. Volnova (IKI) report on behalf of IKI-GRB-FuN:

We continue observations of the OT (Pozanenko et al., GCN 27276) 
associated with GRB 200228B (Laha et al., GCN 27254; Fermi GBM Team, GCN 
27253) with AZT-33IK 1.5-m telescope of Sayan observatory (Mondy) and 
AS-32 telescope of Abastumani Astrophysical observatory. The OT is well 
observable (see photometry below in the table) and current XRT position 
( https://www.swift.ac.uk/xrt_positions/00958733/ ) coincides with 
position of the OT.

Preliminary photometry of the object following.

Date UT start       t-T0  Filter Exp. OT Err UL(3sigma)   telescope
                         (mid, days) (s)
2020-03-03 01:36:36 3.6186   R 58*60  21.65 0.13  22.6 AS-32
2020-03-03 21:03:33 4.4228   R 20*120 22.2  0.4   22.0 AZT-33IK
2020-03-04 23:44:59 5.5488   R 80*60  21.93 0.17  22.6 AS-32

Photometry is based on the USNO-B2.0 nearby stars used in previous 
observations (GCN 27276).

The light curve in R-filter is available at 
http://grb.rssi.ru/GRB200228B/GRB200228B_lc_2.png

We urge on spectroscopic and multicolor photometry to classify the OT.