[vsnet-grb-info 18848] GRB 161219B: GROND afterglow observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  20299
SUBJECT: GRB 161219B: GROND afterglow observations
DATE:    16/12/20 07:57:56 GMT
FROM:    Thomas Kruehler at MPE Garching  <kruehler at mpe.mpg.de>

T. Kruehler, P. Wiseman and J. Greiner (all MPE Garching) report on
behalf of the GROND team:

We observed the field of GRB 161219B (Swift trigger 727541; D'Ai,
GCN #20296) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.
2008, PASP 120, 405) mounted at the 2.2m MPG telescope at the ESO
La Silla Observatory (Chile).

Observations started at 01:33 UT on 2016-12-20, 6.7 hr after the GRB
trigger. They were performed at an average seeing of 1".1, and at an
average airmass of 1.3.

Based on combined images with 14.5 min of total exposures in g'r'i'z'
and 12.0 min in JHK at a mid-time of 01:42 UT on 2016-12-20,
we derive the following preliminary magnitudes (all in AB system)
for the optical/NIR afterglow (D'Ai et al., GCN 20296).

g' = 18.04 +- 0.05 mag
r' = 18.08 +- 0.05 mag
i' = 17.98 +- 0.05 mag
z' = 17.88 +- 0.05 mag
J = 17.68 +- 0.05 mag
H = 17.57 +- 0.07 mag
K = 17.54 +- 0.08 mag

Given magnitudes are calibrated against Pan-STARRS/2MASS field stars
and are not corrected for the expected Galactic foreground extinction
corresponding to a reddening of E_(B-V) = 0.028 mag in the direction of
the burst (Schlafly & Finkbeiner 2011).

We note the presence of a bright (r=21 mag) and visibly extended galaxy
in the Pan-STARRS data at the position of GRB 161219B. This is likely
the host galaxy of the GRB and would, if confirmed, indicate a
relatively low redshift.