TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3021 SUBJECT: GRB050215A: ROTSE-III Optical Observations DATE: 05/02/15 03:45:25 GMT FROM: Don Smith at U michigan Title: GRB050215A: ROTSE-III Optical Observations Smith, D. A., Rykoff, E. S., & Yost, S. A. (U. of Michigan) report on behalf of the ROTSE collaboration: ROTSE-IIIb, located at McDonald Observatory, Texas responded to Swift GRB050215A (Trigger #106106). An automatic response resulted in a sequence of 29 images beginning 7.2 seconds after receipt of the GCN trigger. The first image was taken at 02:16:34.2, 65.7 sec after the burst trigger. The source was fairly low on the horizon and setting. We took 10 5-s, 10 20-s and 9 60-s exposures before the alert for GRB 050215B (Trigger #106107) interrupted the sequence (See Yost et al., coming soon) The images are unfiltered and were calibrated relative to USNO A2.0. As the source is in a crowded field at relatively low galactic latitude, our limits are adversely effected by source confusion. Individual images have limiting magnitudes ranging from 15.9-17.4. Comparison to DSS (second epoch) reveals no new sources within the 3-sigma error circle to a limiting magnitude of 17.4 and 17.6 for co-adds of 10 images taken between 66 s and 18 min after the burst.