[vsnet-grb-info 11156] GRB 111117A: GROND observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  12568
SUBJECT: GRB 111117A: GROND observations
DATE:    11/11/18 11:02:44 GMT
FROM:    Alexander Kann at TLS Tautenburg  <kann at tls-tautenburg.de>

S. Schmidl, A. Rossi, D. A. Kann, (all TLS Tautenburg) and J. Greiner (MPE
Garching) report on behalf of the GROND team:

We observed the field of GRB 111117A (Swift trigger #507901, Mangano et al.,
GCN 12559) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2 m MPI/ESO telescope at La Silla
Observatory (Chile).

Observations started at 02:01 UT on November 18, 13.8 hr after the GRB
trigger. They were performed at an average seeing of 1".8 and an average
airmass of 1.7 .

We detect the afterglow/host candidate that was reported by Andersen et
al. (GCN 12563, R = 23.1 ± 0.3), Fong et al. (GCN 12566, r = 23.9 ± 0.15)
and Cucchiara et al. (GCN 12567, r' = 23.99 ± 0.11) in the g' and r' band.

Based on the first 75 min of total exposures in g'r'i'z' and 60 min in
JHK, we estimate preliminary magnitudes (all in AB system) of

g' = 24.08 ± 0.15,

r' = 24.08 ± 0.16,

i' > 23.9,

z' > 23.4,

J  > 21.7,

H  > 21.3 and

K  > 19.5.

Our r'-band magnitude is in agreement with Fong et al. and Cucchiara et al.

Magnitudes are calibrated against SDSS as well as 2MASS field stars
and are not corrected for the expected Galactic foreground extinction
corresponding to a reddening of E_(B-V)=0.03 mag in the direction of the
burst (Schlegel et al. 1998).