[vsnet-grb-info 16493] GRB 150428A: Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17774
SUBJECT: GRB 150428A: Swift-BAT refined analysis
DATE:    15/04/28 12:49:41 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto at phys.aoyama.ac.jp>

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

Using the data set from T-239 to T+963 sec from the recent telemetry downlink, 
we report further analysis of BAT GRB 150428A (trigger #639275) 
(Page, et al., GCN Circ. 17765).  The BAT ground-calculated position is 
RA, Dec = 188.539, 6.967 deg which is 
  RA(J2000) =   12h 34m 09.3s 
  Dec(J2000) = +06d 58' 00.8” 
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). 
The partial coding was 16%. 

The mask-weighted light curve shows a multi-peaked structure that starts at 
~ T-40 sec and ends at ~ T+60 sec.  T90 (15-350 keV) is 53.2 +- 15.1 sec 
(estimated error including systematics). 

The time-averaged spectrum from T-39.0 to T+38.6 sec is best fit by a simple 
power-law model. The power law index of the time-averaged spectrum is 1.28 +- 0.09. 
The fluence in the 15-150 keV band is 6.3 +- 0.3 x 10^-6 erg/cm2.  The 1-sec peak 
photon flux measured from T+17.4 sec in the 15-150 keV band is 3.0 +- 0.5 ph/cm2/sec.  
All the quoted errors are at the 90% confidence level.  

The results of the batgrbproduct analysis are available at 
http://gcn.gsfc.nasa.gov/notices_s/639275/BA/