TITLE:   GCN CIRCULAR
NUMBER:  17519
SUBJECT: GRB 150301A: Swift-BAT refined analysis
DATE:    15/03/01 22:13:47 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

T. Sakamoto (AGU), S. D. Barthelmy (GSFC),  W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-210 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 150301A (trigger #632995)
(Lien, et al., GCN Circ. 17510).  The BAT ground-calculated position is
RA, Dec = 244.281, -48.732 deg which is
  RA(J2000)  =  16h 17m 07.5s
  Dec(J2000) = -48d 43' 56.2"
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 96%.

The mask-weighted light curve shows a single short FRED peak that starts at
~ T0 and ends at ~ T+0.5 s. T90 (15-350 keV) is 0.48 +- 0.14 sec (estimated error
including systematics).

The time-averaged spectrum from T+0.00 to T+0.56 sec fit by a simple power-law
model has a power law index of 1.44 +- 0.23 (chi squared 54.10 for 57 d.o.f.).
The fluence in the 15-150 keV band is 7.4 +- 1.0 x 10^-8 erg/cm2.
The 1-sec peak photon flux measured from T-0.22 sec in the 15-150 keV band
is 1.0 +- 0.2 ph/cm2/sec.

A single blackbody fit to the time-averaged spectrum shows a blackbody
temperature of 15.11 +- 2.92 keV (chi squared 74.66 for 57 d.o.f.).
A thermal bremsstrahlung model fit shows the temperature of 199.36 keV
(chi squared 55.72 for 57 d.o.f.).

Despite being near the Galactic Plane and Bulge (lat = 1.36, lon = 334), both the
fast-decaying XRT light curve and Fermi/GBM observation (Connaughton et al.,
GCN Circ. 17511) suggests that this source is more likely to be a short GRB than
a SGR. In addition, there are no other BAT detections of this source before or since
this trigger.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/632995/BA/