[vsnet-grb-info 19896] GRB 171007A: Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21981
SUBJECT: GRB 171007A: Swift-BAT refined analysis
DATE:    17/10/08 16:57:32 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien at nasa.gov>

S. D. Barthelmy (GSFC), J. K. Cannizzo (NASA/UMBC),
J. R. Cummings (CPI), H. A. Krimm (NSF/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
J. P. Norris (BSU), 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 171007A (trigger #777215)
(Cannizzo et al., GCN Circ. 21976).  The BAT ground-calculated position is
RA, Dec = 135.635, 42.930 deg which is
  RA(J2000)  =  09h 02m 32.5s
  Dec(J2000) = +42d 55' 47.4"
with an uncertainty of 3.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve shows a short spike that start at ~ T-0.1 s and
ends at ~ T+2.9 s. There is some weak emission lasting till ~T+80 s.
T90 (15-350 keV) is 105 +- 45 sec (estimated error including systematics).

The time-averaged spectrum from T-0.08 to T+107.92 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.38 +- 0.52.  The fluence in the 15-150 keV band is 2.9 +- 1.1 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.92 sec in the 15-150 keV band
is 0.4 +- 0.1 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

Although the burst is weak and the short spike is ~ 3 s, the structure of the burst
shows similarity to those of short GRBs with extended emission. We thus perform
further analysis on the short spike and the tail emission. The spectrum of the short
spike from T-0.08 to T+2.92 sec is best fit by a simple power-law model, with
power-law index of 0.83 +- 0.35 and fluence (15-150 keV) of 1.0 +- 0.2 x 10^-7 erg/cm2.
The spectrum of the tail emission from T+2.92 to T+107.92 sec is best fit by a simple
power-law model, with power-law index of 1.67 +- 0.73 and fluence (15-150 keV) of
1.8 +- 1.0 x 10^-7 erg/cm2. These values are consistent with those of short GRBs with
extended emission (Lien & Sakamoto et al. 2016).

The lag analysis is unconstrained due to the weakness of this burst.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/777215/BA/