GCN Circular 23371
Subject
GRB 181022A: GROND upper limits
Date
2018-10-23T12:07:26Z (6 years ago)
From
Patricia Schady at Swift <p.schady@bath.ac.uk>
P. Schady (Univ. of Bath) and J. Bolmer (MPE, Garching) report:
We observed the field of GRB 181022A (Swift trigger 868312; Marshall et al., GCN #23364) 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 01:53 UT on 2018-10-23, 8.4 hrs after the GRB trigger. They were performed at an average seeing of 1.4" and average airmass of 1.8.
Based on a total of 16 mins integration time, we do not detect a source within the Swift-XRT error circle reported by Marshall et al. (GCN #868312) down to the following 3 sigma AB magnitudes:
g' > 22.8 mag
r' > 22.9 mag
i' > 22.7 mag
z' > 22.5 mag
J > 21.3 mag
H > 20.8 mag
K > 18.9 mag
The given limits are derived based on calibrating the images against GROND zeropoints and 2MASS field stars and are not corrected for the Galactic foreground extinction corresponding to a reddening of E_(B-V)= 0.01 in the direction of the burst (Schlafly & Finkbeiner 2011).
We thank Markus Rabus for the excellend support from La Silla.