GCN Circular 15493

GRB 131117A: GROND confirmation of the afterglow and  photo-z.

M. Tanga (MPE Garching), S. Schmidl, S. Klose (both TLS Tautenburg), K.
Varela (MPE Garching) and J.Greiner (MPE Garching) report on behalf of the
GROND team:

We observed the field of GRB 131117A (Swift trigger 577968, Page et al.,
GCN 15490
Not found
 
 
) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2m MPG telescope at ESO La Silla
Observatory (Chile).

Observations started on November 17, 2013, at 00:36:34 UT, 150 s after the
GRB trigger. They were performed at an average seeing of 1".0 and at an
average airmass of 1.2 .

We detect the fading afterglow discovered by Trotter et al. (GCN 15491
Not found
 
 
).

Based on a total exposure time of 460 s in g'r'i'z' and 480 s in JHK, at a
midtime of 0.80 hrs after the burst, we measure the following preliminary
AB magnitudes:

g' = 20.9 +/- 0.1,
r' = 19.6 +/- 0.1,
i' = 19.1 +/- 0.1,
z' = 19.0 +/- 0.1,
J =  19.0 +/- 0.1,
H =  18.9 +/- 0.1 and
K =  18.7 +/- 0.3.

Given magnitudes are calibrated against GROND zeropoints as well as 2MASS
field stars and are not corrected for the expected Galactic foreground
reddening of E(B-V) = 0.02 mag in the direction of the burst (Schlegel et
al. 1998).

On the basis of the preliminary analysis we estimate the photometric
redshift to be z = 4.18 +/-0.16.