[vsnet-grb-info 19505] GRB 170607B: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21238
SUBJECT: GRB 170607B: Fermi GBM detection
DATE:    17/06/09 19:27:07 GMT
FROM:    Rachel Hamburg at UAH  <rkh0007 at uah.edu>

R. Hamburg (UAH), C. Meegan (UAH), and E. Bissaldi (Politecnico & INFN Bari)
report on behalf of the Fermi GBM Team:

"At 22:41:58.95 UT on 07 June 2017, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 170607B (trigger 518568123 / 170607946)
which was also detected by the AstroSat CZTI
(Sharma et al. 2017, GCN 21232).

The on-ground calculated location, using the GBM trigger
data, is RA = 257.1, DEC = -35.7, with an uncertainty
of 1.5 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 99
degrees.

The GBM light curve consists of a spiked structure
with a duration (T90) of about 18 s (50-300 keV).
The time-averaged spectrum from T0-5.1 s to T0+22.5 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.77 +/- 0.02 and
the cutoff energy, parameterized as Epeak, is 627 +/- 21 keV.

The event fluence (10-1000 keV) in this time interval is
(5.9 +/- 0.1)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+20.4 s in the 10-1000 keV band
is 12.0 +/- 0.4 ph/s/cm^2.

A Band function fits the spectrum equally well
with Epeak= 619 +/- 22 keV, alpha = -0.76 +/- 0.02 and beta =
-3.5 +/- 0.7.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."