TITLE: GCN CIRCULAR NUMBER: 15493 SUBJECT: GRB 131117A: GROND confirmation of the afterglow and photo-z. DATE: 13/11/17 06:17:20 GMT FROM: Mohit Tanga at MPE/GROND 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) 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). 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.