TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2597 SUBJECT: GRB040511: Candidate optical/NIR afterglow DATE: 04/05/14 01:51:23 GMT FROM: Derek Fox at CIT D.B. Fox, E. Berger and D. Moon (Caltech), with K. von Braun and B. Lee (Carnegie), report: "We have imaged the SXC localization region for GRB040511 (Dulligan et al., GCN 2588) in the J-band with the Dupont telescope + WIRC imager at Las Campanas Observatory, on two occasions. Our first-night imaging consists of 21 minutes' exposure at mean epoch May 12.05 UT (12.2 hours post-burst) in 1" seeing; our second-night imaging consists of 15 minutes' exposure at mean epoch May 13.35 UT (43.4 hours post-burst) in 0.75" seeing. PSF-matched image subtraction of the combined images from these two nights reveals a single source within the SXC region that fades significantly between the two epochs, from J~19.0 mag to J~20.9 mag as referenced to 2MASS photometry of the field. Since the source is also observed to fade (by ~1.3 mag) in the contemporaneous (t+11 hour and t+36 hour, respectively) R-band imaging of Morrell et al. (GCN 2594) and Chen et al. (GCN 2591), we conclude that it is a likely afterglow candidate. The source coordinates are: RA 14:47:49.33, Dec -44:14:21.8 (J2000) as referenced to 2MASS catalog astrometry; the uncertainty in this position is < 0.5". The image-pixel coordinate position of the candidate on the first-epoch imaging of Chen et al. (see http://www.graasp.org/, "DATA" section, file "grb040511_R1.fits") is X=1214.6, Y=1463.8. The authors would like to express their gratitude to the the Carnegie Supernova Program for this allocation of time, and to the GRAASP collaboration for the public release of their data in FITS format.