[vsnet-grb-info 18386] GRB 160821B: NOT optical afterglow candidate

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19834
SUBJECT: GRB 160821B: NOT optical afterglow candidate
DATE:    16/08/22 02:30:07 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu at nao.cas.cn>

D. Xu (NAOC/CAS), D. Malesani (DARK/NBI and DTU Space), A. de Ugarte 
Postigo (IAA-CSIC, DARK/NBI), E. Gafton, I. Rivero Losada (NOT) report 
on behalf of a larger collaboration:

We observed the field of the short GRB 160821B (Siegel et al., GCN 
19833) using the 2.56-m Nordic Optical Telescope (NOT) equipped with the 
ALFOSC camera. Observations started at 23:02:07 UT on 2016-08-21 (i.e., 
0.548 hr after the burst), and 12 x 300s SDSS r-band frames were 
obtained under variable cirrus.

We detected an uncatalogued point source at coordinates:

R.A. = 18:39:54.56
Dec. = +62:23:30.5

with an uncertainty radius of ~0.2 arcsec, which is within the XRT error 
circle reported in Siegel et al. (GCN 19833). This source had 
R=22.6+/-0.1 mag at 0.95 hr after the burst, calibrated against the star 
of R = 17.6 at RA = 18:39:57.59, Dec = +62:22:31.7 in the USNO B1 catalogue.

We also note the presence of a bright, extended, nearby galaxy, 5.5" 
away, with a magnitude R ~ 19.2, which is a candidate host galaxy of GRB 
160821B.

Lacking variability, we cannot confirm whether the source we identified 
is the afterglow of GRB 160821B. Further observations are encouraged.