[vsnet-grb-info 18181] GRB 160625A: GROND upper limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19629
SUBJECT: GRB 160625A: GROND upper limits
DATE:    16/06/30 11:29:31 GMT
FROM:    Ting-Wan Chen at MPE  <jchen at mpe.mpg.de>

T. Schweyer, T.-W. Chen, and J. Greiner (all MPE Garching) report on behalf of the GROND team:

We observed the field of GRB 160625A (Swift trigger 701503; Maselli et al., GCN #19577) 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 22:55 UT on 2016-06-26, 24.24 hrs after the GRB trigger.
They were performed through cirrus at an average seeing of 1.4" and at an average airmass of 1.2.

We do not detect any source within the Swift-XRT error circle reported by Burrows et al. (GCN #19578) down to

g > 22.6 mag,
r > 23.9 mag,
i > 22.5 mag,
z > 22.6 mag,
J > 19.9 mag,
H > 19.4 mag,
K > 19.5 mag.

Given magnitudes are calibrated against USNO as well as 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=1.2 mag in the direction of the burst (Schlafly and Finkbeiner 2011).