J. Cummings (GSFC/NRC), L. Barbier (GSFC), S. Barthelmy (GSFC),
E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (UMD),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS),
M. Suzuki (Saitama), M. Tashiro (Saitama U.), J. Tueller (GSFC),
on behalf of the Swift/BAT team:
At 09:25:40 UT, the Swift Burst Alert Telescope (BAT) triggered
and located GRB050502B (trigger=116116) (GCN Circ 3330, Falcone
et al.). The refined BAT ground position is (RA,Dec) = 142.543,
+17.002, [deg; J2000] +- 3 arcmin, (95% containment). This is
24 arc seconds from the position determined by the XRT (GCN Circ
3333, Pagani, et al.). The burst was 10 degrees off the Swift
boresight, within the fully-coded BAT field of view.
The BAT mask-weighted light curve shows one main peak of about 6
seconds duration centered at the trigger time preceded by two
smaller peaks 16 and 10 seconds earlier with a softer spectrum.
T90 (15-350 keV) is (17.5 +- 0.2) seconds (estimated error
The spectrum is well fit by a single power law with photon index
of 1.6 +- 0.1. The fluence in the 15-350 keV band is
(8.0 +- 1.0) x 10^-7 erg/cm2. The peak photon flux in the 15-350
band is (1.73 +- 0.15) ph/cm2/s. All the quoted errors are at the
90% confidence level.
We note that this burst appears to be well-suited for ground
follow-up observations, as it is located 90 degrees from the Sun,
180 degrees from the Moon, close to the ecliptic, and away from
the Galactic center.