GCN Circular 3385
Subject
GRB 050509b: Swift-BAT refined analysis of the short hard burst
Date
2005-05-09T07:06:49Z (20 years ago)
From
Scott Barthelmy at NASA/GSFC <Scott@lheamail.gsfc.nasa.gov>
S. Barthelmy (GSFC), L. Barbier (GSFC), J. Cummings (GSFC/NRC),
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), J. Tueller (GSFC), T. Mitani (ISAS),
F. Marshall (GSFC), T. Takahashi (ISAS)
on behalf of the Swift/BAT team:
At 04:00:19.23 UT Swift-BAT detected GRB 050509b (trigger=118749)
(GCN Circ 3381, C. Hurkett et al.). The refined BAT ground position
is (RA,Dec) = 189.073,+28.991 {12:36:18,28:59:28} +- 2.8 arcmin [deg; J2000],
(95% containment). This is 59 arcsec from the XRT position (Kennea et al.,
GNC 3383). The burst was in the fully-coded FOV. Using the event-by-event
data, the lightcurve shows a single spike with a duration of ~30msec.
Further, the hardness ratio S(50-100)/S(25-50) of ~1.5 puts this burst cleanly
in the short-hard cluster on the hardness_ratio vs duration scatter-plot.
Using a simple power-law model, the photon index of the time-averaged
spectrum is 1.5 +- 0.4. The fluence in the 15-350 keV band is
(2.3 +- 0.9) x 10^-8 erg/cm2. The 1-s peak photon flux
in the 15-350 band is (1.57 +- 0.36) ph/cm2/s.
All the quoted errors are at the 90% confidence level.
We note that location is consistant with the galaxy cluster NSC J123610+285901
which has a redshift of z=0.22, which roughly translates to a distance
of ~1 Gpc. We also note that at this distance and the observed flux,
this is is an order of magnitude farther than the 27-Dec-04 SuperFlare
event from SGR1806-20 could be seen.