TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2681 SUBJECT: GRB 040827: Detection of NIR afterglow DATE: 04/08/28 02:32:35 GMT FROM: Edo Berger at Carnegie Obs M. Gladders and E. Berger (Carnegie Observatories) report: "We imaged a portion of the 2.5-arcmin error circle of GRB 040827 (GCN #2672), centered on the XMM-Newton X-ray source (GCN #2678), with the PANIC instrument on the Magellan Baade 6.5-m Telescope. A total of 36 minutes were obtained in the Ks-band under good weather conditions with a seeing of about 0.55". Within the 10-arcsec XMM error circle we find two sources with a magnitude of Ks~19.8+/-0.2 mag (XMM-1) and Ks~19.4+/-0.15 mag (XMM-2) compared to 2MASS. The positions of the two source are (J2000): RA= 15:17:01.43 DEC= -16:08:22.7 (XMM-1) and RA= 15:17:01.35 DEC= -16:08:28.6 (XMM-2) Source XMM-1 coincides with the I-band source reported by Berger, Thompson and Krzeminski (GCN #2680), while source XMM-2 appears to be extended. We therefore conclude that XMM-1 is the likely optical/NIR afterglow of GRB 040827. A comparison of the Ks- and I-band magnitudes indicate a spectral index beta~-0.5 typical of GRB afterglows."