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GCN Circular 15289

Subject
Swift J1242.9-3530, Swift-BAT refined analysis
Date
2013-10-02T18:43:17Z (11 years ago)
From
Jay R. Cummings at NASA/GSFC/Swift <james.r.cummings@nasa.gov>
J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
A. Y. Lien (NASA/GSFC/ORAU), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC),
T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):

Using the data set from T0 to T+1699 sec from the recent telemetry downlink,
we report further analysis of Swift J1242.9-3530 (formerly cited as GRB 130930A,
BAT trigger #572489) (Ukwatta, et al., GCN Circ. 15276).  The BAT ground-
calculated position is RA, Dec = 190.725, -35.511, which is
RA (J2000)      12h 42m 53.9s
Dec (J2000)     -35d 30' 40"
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 86%.

The mask-weighted light curve varies slowly over the duration of the observation.
The emission appears to extend before and after the observation so we cannot
determine a T90 interval.

The time-averaged spectrum from T0 to T0+1699 sec is best fit by a simple power-
law model.  The power-law index of the time-averaged spectrum is 1.90 +- 0.18.
The fluence in the 15-150 keV band is (3.9 +/- 0.4) x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.00 sec in the 15-150 keV band
is 0.036 +- 0.004 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The source is also detected at a similar intensity in ground analysis of an
earlier observation, from T0-46108 to T0-44561 seconds, but is not detected
in an observation with a similar pointing from T0-51899 to T0-50201 seconds.
The 90% confidence upper limit is 0.2 times the intensity observed later.
We note that the location of the source is 27 degrees from the Galactic plane
and not in the direction of the Galactic center.

The narrow-field instruments of Swift cannot observe this location until late
November at the earliest due to the proximity of the Sun.

The data included in the automated analysis covers only T-239 to T+963 seconds.
The results of the batgrbproduct automated analysis will be available if the US
government ever returns to normal operations at
http://gcn.gsfc.nasa.gov/notices_s/572489/BA/
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