TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3981 SUBJECT: GRB050915: P60 Optical Observations DATE: 05/09/15 13:54:17 GMT FROM: S. Bradley Cenko at Caltech S. Bradley Cenko (Caltech) and Derek B. Fox (Penn State) report on behalf of a larger collaboration: We have imaged the error circle of GRB 050915 (Grupe et al., GCN 3977) with the automated Palomar 60-inch telescope. Observations began approximately 4 minutes after the burst in the Kron R and Gunn i filters. Inside the XRT error circle (Kennea et al., GCN 3979), we find no source present. Using the USNO-B object located at 05:26:48.6, -28:00:48.9 (J2000.0, R2 = 17.90, I2 = 17.88) as a reference, we find the following 3-sigma upper limits for any point-source in the XRT error circle: Filter Int Time (s) Mean UT Tb (min) Mag --------------------------------------------------------------------------- R 540 11:41 18 > 21.0 i 540 11:43 20 > 20.5