[vsnet-grb-info 18109] GROND observations of GRB 160622A/SNR RCW 103/SGR 1617-5103

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19557
SUBJECT: GROND observations of GRB 160622A/SNR RCW 103/SGR 1617-5103
DATE:    16/06/23 19:42:07 GMT
FROM:    Alexander Kann at TLS Tautenburg  <kann at tls-tautenburg.de>

D. A. Kann (TLS Tautenburg), P. Schady, and J. Greiner (both MPE Garching)
report on behalf of the GROND team.

We observed the field of GRB 160622A/SNR RCW 103/SGR 1617-5103 (Swift
trigger 700791; D'Ai et al., GCN #19547) 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 02:19 UT, 0.26 hrs after the GRB trigger, and 
continued for around 1 hr. They were performed at an average seeing of
1".4 and at an average airmass of 1.

In stacked data amounting to about 30 min exposure time in g'r'i'z' and
about 15 min in JHK, we do not detect any sources within the enhanced
Swift-XRT error circle (Evans et al., GCN #19551) down to the following 3
sigma upper limits (AB magnitudes):

g� > 23.4 mag,
r' > 23.3 mag,
i' > 23.1 mag,
z' > 23.0 mag,
J > 19.8 mag,
H > 18.9 mag, and
K > 18.7 mag.

We detect two sources just outside the XRT error circle. One to the south,
which is likely a blended double source, and a faint source to the west.
The PSF wing of the southern source lies within the XRT error circle,
reducing our limiting magnitude there.

Given magnitudes are calibrated against GROND zeropoints as well as 2MASS
field stars and are not corrected for the very high expected Galactic
foreground extinction in the direction of the burst (Schlafly &
Finkbeiner, 2011).