[vsnet-grb-info 21323] GROND observations of GRB181110A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23422
SUBJECT: GROND observations of GRB181110A
DATE:    18/11/11 13:17:04 GMT
FROM:    Jan Bolmer at MPE/Garching  <jan at bolmer.de>

J. Bolmer (MPE, Garching) and P. Schady (Univ. of Bath) report:

We observed the field of GRB 181110A (Swift trigger 871316; Evans et al., GCN #23413)
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 00:01 UT, 15.5 hrs after the GRB trigger, and were performed
under poor seeing conditions, 4.1“, and at an average airmass of 1.2.

We detect a source at a position consistent with the X-ray and optical afterglow
(Evans et al., GCN #23413; Kuin et al., GCN #23419). Based on the first 17 min of
total exposures in g'r'i'z' and 20 min in JHK, we measure the following preliminary
AB magnitudes:

g' = 21.25 +/- 0.06 mag
r' = 20.58 +/- 0.05 mag
i' = 19.91 +/- 0.08 mag
z' = 20.08 +/- 0.09 mag
J = 20.16 +/- 0.20 mag
H = 19.76 +/- 0.18 mag
K = 19.27 +/- 0.18 mag

Given magnitudes are calibrated against USNO and 2MASS field stars and are not corrected
for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.06
in the direction of the burst (Schlafly & Finkbeiner 2011).