GCN Circular 20630
Subject
GRB 170207A: Fermi GBM observation
Date
2017-02-08T18:17:45Z (8 years ago)
From
Oliver J Roberts at USRA/NASA <oliver.roberts@nasa.gov>
O.J. Roberts (USRA/NASA), B. Mailyan (UAH) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:
"At 21:45:03.67 UT on February 7th 2017, the Fermi Gamma-Ray
Burst Monitor triggered and located GRB 170207A
(trigger 508196708 /170207906). This event was also detected
by Konus Wind (Svinkin et al, GCN 20629) and localized by the
IPN (Svinkin et al, GCN 20628). The on-ground calculated location
using the GBM trigger data is,
RA = 325.87, DEC = +50.05 (J2000 degrees), equivalent to
J2000 21h 43m, +50d 03',
with an uncertainty of 1 degree (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 initial angle from the Fermi-LAT boresight to the GBM
ground-location is 94 degrees.
The GBM light curve shows a long burst with multiple
episodes of bright emission over a duration (T90) of about
39 s (50-300 keV). The time-averaged spectrum from T0+0 s to
T0+39 s is best fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.92 +/- 0.02 and
the cutoff energy, parameterized as Epeak, is 499.4 +/- 19.5 keV.
A Band function fits the spectrum equally well, with
alpha= -0.91 +/- 0.02, beta= -2.68 +/- 0.28 and Epeak
is 478.8 +/- 23.1 keV.
The event fluence (10-1000 keV) in this time interval is
(5.86 +/- 0.07) E-05 erg/cm^2. The 1s peak photon flux
measured starting from T0+20.5 s in the 10-1000 keV band is
25.4 +/- 0.4 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."