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GCN Circular 21995

GRB 171010B: Swift detection of a burst
2017-10-11T19:18:11Z (7 years ago)
Amy Lien at GSFC <>
D. M. Palmer (LANL) and A. Y. Lien (GSFC/UMBC),
report on behalf of the Swift team:

At 20:59:24.168 UT on 2017-10-10, the Swift Burst Alert Telescope (BAT) triggered on
GRB 171010B (trigger=778019). However, on-board analysis was truncated by
a pre-planned slew to a scheduled target.  Subsequent ground analysis
using data from T+1 to T+11 s finds the source at a location of
RA, Dec = 34.123, -54.410 deg which is 
  RA(J2000)  =  02h 16m 29.6s 
  Dec(J2000) = -54d -24' -36.7" 
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 71%.

The BAT light curve shows a single-peaked structure that starts and peaks at ~T0, 
and ends at ~ T+30 s. Because the burst was not identified on board, the event 
data available (~T+1 to ~T+11) do not cover the entire burst duration.
T90 estimated from the BAT raw light curve (15-350 keV) is about 30.4 s.

The time-averaged spectrum from T+1.0 to T+11.1 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.41 +- 0.18.  The fluence in the 15-150 keV band is 3.9 +- 0.5 x 10^-7 erg/cm2.
All the quoted errors are at the 90% confidence level.

This event was also detected by Fermi/GBM (trigger 529361971).

A Swift Target of Opportunity observation has been requested.

The results of the batgrbproduct analysis are available at
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