[vsnet-grb-info 27105] GRB 201227A: Chilescope optical observations, possible optical counterpart

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29208
SUBJECT: GRB 201227A: Chilescope optical observations, possible optical counterpart
DATE:    20/12/30 21:14:02 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

S. Belkin (IKI), A. Pozanenko (IKI), M. Krugov (FAI), P. Minaev (IKI) 
report on behalf of GRB IKI FuN collaboration:

We observed the field of XRT 1-3 sources (D'Elia et al., GCN 29202)
(hereafter X1,X2,X3) found in IPN localization area (Svinkin et al.,
GCN 29182) of GRB 201227A (Ursi et al., GCN 29179; Xiao et al., GCN
29187; Svinkin et al., GCN 29196; Lesage et al., GCN 29206) with
Chilescope RC-1000 starting on 2020-12-29 (UT) 04:02:05 in r'-filter.

The X3 source was observed by one 300 s exposure, and the filed of X1,X2
was observed by 3*300 s exposure. The limiting magnitude of single
exposure of X3 and the stacked 3*300 s exposure is about r'=20.9.

There are two optical sources close or on the edge of the XRT error 
circle localization of X3. Both sources are present in USNO-B1.0 and our 
photometry of the sources show no excess in brightness in comparison
with any R-mag of USNO-B1.0.

Also there are two optical sources close or on the edge of the XRT error
circle localization of X1. Both source are also present in USNO-B1.0 and
our photometry of the sources show no excess in brightness in comparison
with any R-mag of USNO-B1.0.

At the edges of X2 error circle we found two sources which not presented
in USNO-B1.0. The coordinates of the first one (X2_O1) is RA(J2000)=11h 
22m 29.34s, Dec(J2000)=-73d 28’ 44.9’’. The photometry of the source is 
r'= 20.50 +/-0.29 and the source is barely visible in DSS2 plate. The 
coordinates of second one (X2_02) is RA(J2000)=11h 22m 27.94s, 
Dec(J2000)=-73d 28’ 50.6’’. The photometry of the source is r'= 20.52 
+/-0.29 and the source is not presented in DSS2 plate. We may suggest 
the optical object X2_02 could be a counterpart of GRB 201227A.

The photometry is based on nearby stars from the APASS_DR8 and still
preliminary

RA DEC r
11:19:31.40904 -73:35:47.6880 14.090
11:19:44.89128 -73:34:49.6092 15.180
11:19:36.65304 -73:36:30.2112 15.307

Taking into account that early more deep observations of the IPN field 
by GRAWITA VST-ESO PARANAL (Izzo et al., GCN 29207) does no show any 
counterpart we  may suggest the X2_O2 source (RA(J2000)=11h 22m 27.936s, 
Dec(J2000)=-73d 28’ 50.55’’) is a possible optical counterpart or 
kilonova of GRB 201227A.