GCN Circular 3021

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.