[vsnet-grb-info 6434] GRB 080727A: Early IR observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8048
SUBJECT: GRB 080727A: Early IR observations
DATE:    08/07/29 15:12:05 GMT
FROM:    Andrew Levan at U.of Leicester  <anl at star.le.ac.uk>

A.J. Levan (U. Warwick) and K. Wiersema (U. Leicester) report for a 
larger collaboration:

We observed the location of GRB 080727A (Immler et al. GCN 
8021) using UKIRT. A series of K-band exposures were taken beginning at
06:24:51 UT, roughly 30 minutes after the burst, a total of 720s
of observtions were taken (36x20s).  We find no evidence for any
source within the XRT error circle (Evans et al. GCN 8025) for GRB
080727A, down to a limit of K=19.8 mag (3-sigma).

Comparing this limit to the extrapolated X-ray flux 30 minutes
post-burst implies that the observed X-ray to optical/IR spectral
slope was beta_KX < ~0.8, thus the non-detection in the IR is likely
down to the rapid fading of the afterglow, rather than suppression
of the optical/IR flux.

We thank the staff of UKIRT for their rapid response to these alerts.