TITLE:   GCN CIRCULAR
NUMBER:  30313
SUBJECT: Fermi GBM observation of a bright burst in the direction of SGR 1935+2154
DATE:    21/06/24 17:38:11 GMT
FROM:    Stephen Lesage at Fermi-GBM Team  <sjl0014@uah.edu>

S. Lesage (UAH) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 02:34:10.19 UT on 24 June 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located a bright, SGR-like burst from the direction of
the magnetar SGR 1935+2154 (trigger 646194855/210624107).

The on-ground calculated location, using the Fermi GBM trigger data, is
RA = 293.73, Dec = 21.90 (J2000 degrees), with a statistical uncertainty
of 2.72 degrees and is consistent with the known position of the SGR.

The angle from the Fermi LAT boresight at the GBM trigger time is 37 degrees.

The burst has a duration (T90) of about 0.08 s (10-300 keV).

It is best fit by a double-blackbody model with temperatures of
kT1 = 7.4 +/- 0.7 keV and kT2 = 13.3 +/- 1.5 keV.

The event fluence (10-300 keV) from T0-0.016s to T0+0.064s is
(1.16 +/- 0.03)E-06 erg/cm^2. The average photon flux in the
10-300 keV band during this period is 194 +/- 4 ph/s/cm^2.

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/"