[vsnet-grb-info 9054] GRB 100322B or possible Galactic transient detected in ground analysis of BAT data

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10542
SUBJECT: GRB 100322B or possible Galactic transient detected in ground analysis of BAT data
DATE:    10/03/23 01:10:54 GMT
FROM:    Jay R. Cummings at NASA/GSFC/Swift  <james.r.cummings at nasa.gov>

J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD),
D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC),
on behalf of the Swift team

At 7:06:18 on March 22, 2010, Swift-BAT detected a rate increase
(trigger #416771).  No source was detected onboard. A source was
detected in ground analysis at RA, Dec 76.489, +42.685, which is:

RA (J2000)   05h 05m 57.4s
DEC (J2000)  +42d 41'07"

with an estimated uncertainty of 4 arcmin (radius, 90% containment).
The source is 1 degree from the Galactic plane, and was 70% coded in
the BAT field of view.

The burst was short, consisting of a single peak with T90 of about
1.5 sec, and weak. The spectrum is best fit by a simple powerlaw with
a photon index of 1.6 +- 0.3.  The fluence from 15-150 keV was
5 +- 3 e-08 ergs/cm2.

While the burst duration and location near the galactic plane are
suggestive of a thermonuclear X-ray burst from a galactic neutron star
X-ray binary, the BAT spectrum argues against that interpretation.
There are about 360 square degrees within 1 degree of the galactic
plane, or ~1% of the entire sky.  Thus, it is certainly plausible for
this burst to be a cosmological GRB.

Because no source was detected onboard, there are no automated data
products.  A Swift TOO has been requested.