TITLE:   GCN CIRCULAR
NUMBER:  27659
SUBJECT: Fermi GBM observation of a bright flare from magnetar SGR 1935+2154
DATE:    20/04/28 02:28:30 GMT
FROM:    Cori Fletcher at USRA  <cfletcher@usra.edu>

C. Fletcher (USRA) reports on behalf of the Fermi GBM Team:

"At 18:26:20.16 UT on 27 April 2020, the Fermi Gamma-Ray Burst
Monitor triggered on a bright, SGR-like burst from the direction
of the magnetar SGR 1935+2154 (trigger 609704785/ 200427768),
which was also detected by the Swift/BAT (Barthelmy et al. 2020, GCN 27657).

The burst has a duration (T90) of ~2 seconds in the energy range 10-200 keV.

It is well-fit by a power law function with an exponential
high-energy cutoff. The power law index is 0.02 +/- 0.68 and
the cutoff energy, parameterized as Epeak, is 27.2 +/- 2.5 keV.

The event fluence (10-200 keV) from T0-1.024 to T0+1.024 is (2.0 +/- 0.2)E-7 erg/cm^2.
The average photon flux in the 10-200 keV band during this period is 2.5 +/- 0.2
ph/s/cm^2.

Fermi GBM also subsequently triggered on multiple bursts from SGR 1935+2154 on
27 April 2020 with a fraction of these being misclassified as GRBs.

The spectral analysis results presented above are preliminary.

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