[vsnet-grb-info 25431] SGR 1935+2154: Fermi GBM observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  27531
SUBJECT: SGR 1935+2154: Fermi GBM observation
DATE:    20/04/10 21:37:38 GMT
FROM:    Peter Veres at UAH  <veresp at gmail.com>

P. Veres (UAH), E. Bissaldi (Politecnico and INFN Bari) and M. S. Briggs
(UAH)
report on behalf of the Fermi GBM Team:

"At 09:43:54.30 UT on 10 April 2020, the Fermi Gamma-Ray Burst Monitor
(GBM) triggered
and located an outburst from SGR 1935+2154 (trigger 608204639 / 200410405)
which was also detected by the Konus-Wind (IPN) (Svinkin at al., GCN
27527). The GBM on-ground location is consistent with the known position of
the SGR.

The trigger was classified as a GRB by the flight software, but it is in
fact from SGR 1935+2154.

The angle from the Fermi LAT boresight at the GBM trigger time is 105
degrees.

The light curve shows a short bright peak with a duration (T90) of about
128 ms (50-300 keV).
The time-averaged spectrum from T0-64 ms to T0+192 ms is best fit by a
power law function with an exponential high-energy cutoff.  The power law
index is 0.70 +/- 0.10 and the cutoff energy, parameterized as Epeak, is
32.7 +/- 0.3 keV

The event fluence (10-1000 keV) in this time interval is (2.57 +/- 0.03)E-6
erg/cm^2. The 64-ms peak photon flux measured starting from T0 in the
10-1000 keV band is 489 +/- 9 ph/s/cm^2.

We note that we see indications of saturation of only the TTE data at the
brightest part of the pulse.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support
Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"