GCN Circular 20652
Subject
GRB 170209A: Fermi GBM Detection
Date
2017-02-09T22:26:43Z (8 years ago)
From
Oliver J Roberts at USRA/NASA <oliver.roberts@nasa.gov>
O.J. Roberts (USRA/NASA) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:
"At 01:08:38.08 UT on the 9th of February 2017,
the Fermi Gamma-Ray Burst Monitor triggered and
located GRB 170209A (trigger 508295323 / 170209048),
for which MASTER reported an OT in follow-up
observations of the reported GBM location region
(Podesta et al. 2017, GCN 20650). The on-ground
calculated location using the GBM trigger data is,
RA = 113.40, DEC = -49.64 (J2000 degrees), equivalent
to J2000 7h 33m, -49d 38',
with an uncertainty of 3.22 degrees (radius, 1-sigma
containment, statistical only; there is additionally
a systematic error which we have characterized as a
core-plus-tail model, with 90% of GRBs having a 3.7 deg.
error and a small tail suffering a larger than 10 deg.
systematic error [Connaughton et al. 2015, ApJS, 216, 32]).
The angle from the Fermi LAT boresight at the GBM trigger
time is 120 degrees.
The GBM light curve consists of a long GRB with two bright
episodes of emission over a duration (T90) of about 40 s
(50-300 keV). The time-averaged spectrum from T0+0 s to
T0+40.0 s is best fit by a power law function with an
exponential high-energy cutoff. The power law index is
-0.95 +/- 0.07 and the cutoff energy, parameterized as
Epeak is 132 +/- 9 keV.
The event fluence (10-1000 keV) in this time interval is
(9.34 +/- 0.37)E-06 erg/cm^2. The 1-sec peak photon flux
measured starting from T0+1.9 s in the 10-1000 keV band
is 12.6 +/- 0.4 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."