GCN Circular 16784
Subject
GRB 140903A: Possible optical variability
Event
Date
2014-09-05T14:49:26Z (12 years ago)
From
Andrew Levan at U.of Leicester <A.J.Levan@warwick.ac.uk>
A.J. Levan (U. Warwick), S.B. Cenko, A. Cucchiara (NASA-GSFC), D.A. Perley (Caltech) report for a larger collaboration:
"We observed the location of the short GRB 140903A (Cummings et al. GCN 16763, 16765) with Gemini-N beginning at 5 Sep 2014, 05:16 UT. At this epoch we obtained observations in iJ and K utilising GMOS-N and NIRI. The source reported by Capone et al. (GCN 16769) and Cenko et al. (GCN 1677) is well detected in all bands.
A comparison between these images and the acquisition images taken on 4 Sept 2014 (Cucchiaria et al. GCN 16774) is indicative of a fading by 0.12 +/- 0.04 mag. An image subtraction shows a residual consistent with this fading, although both photometry and image subtraction are complicated by the presence of the nearby bright star.
This decay is very slow in comparison to most GRB afterglows and implies a significant contribution from the underlying host galaxy, consistent with its pre-trigger detection (Fruchter GCN 16776, Xu et al. GCN 16783). We note that the source remains largely point like in our observation, and the centroid of the subtraction residual is offset only ~0.1" from the centre of the combined host+afterglow source."