TITLE: GCN CIRCULAR NUMBER: 17745 SUBJECT: GRB 150424A: Keck detection of optical afterglow DATE: 15/04/24 10:19:56 GMT FROM: Daniel Perley at Caltech D. A. Perley (Caltech) and N. J. McConnell (IfA) report: We observed the field of short-duration GRB 150424A (Beardmore et al., GCN 17743) with the Low Resolution Imaging Spectrometer (LRIS) on the Keck I 10m telescope. Three 120-second imaging exposures in g- and R-bands were acquired between 09:15 and 09:26 UT (approximately 1.6 hours after the GRB trigger), at low elevation through moderate cloud cover. In both filters we detect a bright (R~20 mag) source, not visible in DSS, at the following location inside the XRT error circle: RA = 10:09:13.381 dec = -26:37:51.50 (+/- 0.5" or less) We suggest this as the optical afterglow of GRB 150424A. We also note the presence of a large galaxy (resolved in DSS) 5 arcsec to the southwest.