GCN Circular 20562

P. Schady, P. Wiseman and J. Greiner (all at MPE Garching) report on behalf of the GROND team:

We observed the field of GRB 170127A (Swift trigger 735326; Markwardt et al., GCN #20538) 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 05:23 UT on 2017-01-27, 15 hrs after the GRB trigger. They were performed at high seeing that varied between 1.5� and 2" and at an average airmass of 1.4.

In combined images with 36 min of total exposures in g�r'i'z' and 30 min in JHK at a mid-time of 05:40 UT on 2017-01-28, we do not detect a source within the Swift-XRT error circle reported by Evans et al. (GCN #20548) down to the following 3 sigma upper limits (all in AB system)

g' > 24.0 mag
r' > 23.7 mag
i' > 23.1 mag
z' > 23.0 mag
J > 20.7 mag
H > 20.3 mag
K > 17.7 mag

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