TITLE: GCN CIRCULAR NUMBER: 17821 SUBJECT: GRB 150514A: GROND Bright Afterglow Confirmation DATE: 15/05/16 00:35:29 GMT FROM: Alexander Kann at TLS Tautenburg R. Yates, F. Knust (both MPE Garching), D. A. Kann (TLS Tautenburg), and J. Greiner (MPE Garching) report on behalf of the GROND team: We observed the field of GRB 150514A (Fermi trigger 453321308; LAT detection: Kocevski et al., GCN # 17816; GBM detection: Roberts et al., GCN # 17819) 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 23:36 UT on 2015-05-15, 29.0 hrs after the GRB trigger. They were performed at an average seeing of 1".5 and at an average airmass of 2.1. Coincident with the UVOT source reported by Marshall & Cannizzo (GCN # 17820), we detect a bright source. Based on 7.7 min of total exposure time in g'r'i'z' and 8 min in JHK centered 29.15 hrs after the GRB, we estimate the following preliminary magnitudes (all in the AB system): g' = 20.5 +/- 0.1 mag, r' = 20.1 +/- 0.1 mag, i' = 19.9 +/- 0.1 mag, z' = 19.6 +/- 0.1 mag, J = 19.2 +/- 0.2 mag, and H = 18.6 +/- 0.2 mag. Compared with the UVOT detections reported by Marshall & Cannizzo (GCN # 17820; 18th magnitude), the source has clearly faded, establishing it as the afterglow of GRB 150514A. We note that similar to other LAT-detected GRBs, this is a very bright afterglow. Spectral follow-up is encouraged. Given magnitudes are calibrated against GROND zero points (g'r'i'z') as well as 2MASS field stars (JHK) and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.02 mag in the direction of the burst (Schlegel et al. 1998).