[vsnet-grb-info 17905] GRB 160422A: GROND NIR afterglow detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19352
SUBJECT: GRB 160422A: GROND NIR afterglow detection
DATE:    16/04/26 11:17:40 GMT
FROM:    Jan Bolmer at MPE/Garching  <jan at bolmer.de>

T. Schweyer, J. Bolmer, J. Greiner (all MPE Garching), and D. A. Kann
(TLS Tautenburg) report on behalf of the GROND team:

We observed the field of GRB 160422A (Fermi/GBM trigger 483019143;
Yassine et al., GCN #19329) simultaneously in g'r'i'z'JHK with GROND
(Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG
telescope at ESO La Silla Observatory (Chile).

Observations started at 23:02 UT on 22-04-2016, 11.06 hrs after the
GRB trigger. They were performed at an average seeing of 2.0" and at
an average airmass of 2.2, but also through thick cirrus, which
prevented proper measurements in g'r'i'z'.

We found a single point source coincident with the 0.45" Swift-UVOT
error circle reported by Marshall et al. (GCN #19333).

Based on the first 4 min of total exposures in JHK, we estimate
preliminary magnitudes (all in AB system) of

J = 17.9 +/- 0.3 mag,
H = 17.4 +/- 0.3 mag, and
K > 17.0 mag.

Given magnitudes are calibrated against 2MASS field stars and are not
corrected for the expected Galactic foreground extinction
corresponding to a reddening of E_(B-V)=0.02 mag in the direction of
the burst (Schlafly & Finkbeiner 2011).