[vsnet-grb-info 19085] GRB 170207A: Fermi GBM observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  20630
SUBJECT: GRB 170207A: Fermi GBM observation
DATE:    17/02/08 18:17:45 GMT
FROM:    Oliver J Roberts at USRA/NASA  <oliver.roberts at 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."