[vsnet-grb-info 9832] MAXI J1659-152: Swift-BAT refined analysis (triggers 434928 and 434931)

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  11300
SUBJECT: MAXI J1659-152: Swift-BAT refined analysis (triggers 434928 and 434931)
DATE:    10/09/25 18:55:41 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at lheamail.gsfc.nasa.gov>

S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), V. Mangano (INAF-IASFPA),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using only a partial data set from T+247 to T+303, T+706 to T+723 and
T+728 to T+963 sec (T=08:05:06 UT) from recent downlinks, we report further analysis
of MAXI J1659-152 (Swift-BAT trigger #434928) (Negoro, ATEL 2873 and
initially reported as GRB 100925A in Mangano, et al., GCN Circ. 11296).
The BAT ground-calculated position is RA, Dec = 254.750, -15.206 deg, which is 
   RA(J2000)  =  16h 59m 00.0s 
   Dec(J2000) = -15d 12' 20.1" 
with an uncertainty of 2.9 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 38%.
 
No statement can be given about the BAT lightcurve because of the fragmented
coverage of the transient.  This fragmentation is caused by (a) a second
Swift-BAT trigger on the same source (a 64-sec image trigger, #434931,
at 09:47:13 UT) and (b) the very long integration time of the first trigger (26.5 min).
The normal set of event-by-event data used to do this "refined" analysis
is not fully available (the on-board event ring buffer has been nearly
completely wrapped).
 
The time-averaged spectrum in the 3 time intervals listed above
is best fit by a simple power-law model.  The power law index
of the time-averaged spectrum is 1.79 +- 0.43.  We caution even this
limited analysis because of the partial coverage of the time interval
of the event. 

Further, the time-averaged spectrum from T+0.0 to T+64.0 sec (T=09:47:13 UT,
the second trigger) is best fit by a simple power-law model.  The power law
index of the time-averaged spectrum is 2.36 +- 0.61.  All the quoted errors
are at the 90% confidence level.

The GCN Notices for the first trigger were distributed with a GRB label,
because the location did not match any known source in the on-board and
ground catalogs.  However, the GCN Notices for the second trigger were
labeled as a transient because the location matched the location of the
first trigger (AT trigger locations are maintained in the on-board catalog
up to the 4th trigger in a 3-deep ring buffer).