GRB 050215A

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.

S. Barthelmy, L. Barbier, J. Cummings (GSFC), E. Fenimore (LANL),
N. Gehrels (GSFC), J. Greiner (MPE), D. Hinshaw (GSFC-SPSYS),
D. Hullinger (GSFC/UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD),
T. Mitani (ISAS), K. Nakazawa (ISAS), J. Norris (GSFC), D. Palmer (LANL),
A. Parsons, T. Sakamoto (GSFC) G. Sato (ISAS), M. Suzuki (Saitama),
J. Tueller (GSFC),  on behalf of the Swift-BAT team:

The BAT instrument on Swift triggered at 02:15:28 and at 02:33:12 UT 15 Feb 05,
triggers 106106 and 106107, respectively.  We have done preliminary analysis
on the ground using the TDRSS messages and the initial portions of the data
from a telemetry downlink.

For GRB050215a (Trigger 106106) the position is RA,Dec=348.382,+49.322 (J2000)
with a position uncertainty of 4 arcmin (statistical plus systematic,
90% containment radius).  The lightcurve is a single peak with a duration
of ~6 seconds.  Nearly all of the emission is in the 15-25 keV band.  The Swift
spacecraft automatically slewed to this burst and began follow-up observations,
but that follow-up sequence was interrupted by the second burst (18 min later).

For GRB050215b (Trigger 106107) the position is RA,Dec=174.450,+40.805 (J2000)
with a position uncertainty of 4 arcmin (statistical plus systematic,
90% containment radius).  The lightcurve is a single peak with a duration
of ~10 seconds.  The emission extends from 15 to ~100 keV.  The Swift spacecraft
also automatically slewed to this burst location and is currently doing
an extended follow-up observation on this burst.  We note that this burst
is well suited for ground-based optical follow-up observations in the Northern
hemisphere.

We note that these bursts are clearly distinct and separate from each other.
It is merely coincidental that these two bursts happened within a few hours
after the enabling of the automatic real-time distribution of the Notices.

A. Breeveld (MSSL), P. Roming (PSU), K. Mason, P. Schady (MSSL), M. 
Ivanushkina (PSU), T. Poole (MSSL), C. Gronwall (PSU), A. Blustin (MSSL), 
P. Brown (PSU), P. Schady, S. Rosen, K. McGowan, M. De Pasquale (MSSL), P. 
Boyd (GSFC/UMBC), S. Holland, M. Still (GSFC/USRA), W. Landsman (GSFC), S. 
Hunsberger (PSU), B. Hancock (MSSL), S. Koch (PSU), M. Carter, H. Huckle 
(MSSL), P. Broos (PSU), T. Kennedy, P. Smith (MSSL), J. Hill (PSU), C. 
Markwardt (GSFC/UMD), T. Sakamoto  (GSFC), J. Nousek (PSU), N. Gehrels 
(GSFC), on behalf of the Swift UVOT team.

The Swift Ultra-Violet/Optical Telescope (UVOT) began observations of 
GRB050215a (GCN 3024
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 ) on February 15, 2005 at 02:17:05 UT.  We detect no 
source down to a magnitude of 19.2 in the UVW2-filter for a 9 second 
exposure starting 98s after the BAT trigger.