[vsnet-grb-info 28304] Fermi GBM Observations of SGR J1935+2154

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30407
SUBJECT: Fermi GBM Observations of SGR J1935+2154
DATE:    21/07/07 16:31:42 GMT
FROM:    Rachel Hamburg at UAH  <rkh0007 at uah.edu>

R. Hamburg (UAH), C. Malacaria (USRA), and C. Fletcher (USRA)
report on behalf of the Fermi GBM Team:

"At 00:33:31.67 UT on 7 July 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located a burst from SGR 1935+2154 (trigger 647310816
/210707023). Bursts from SGR 1935+2154 have been recently reported
by Integral/IBAS (Mereghetti et al. 2021, GCN 30395), GECAM-B
(Xiao et al. 2021, GCN 30400), and Swift/BAT (Palmer et al. 2021, GCN
30406).
The GBM on-ground location is consistent with the known position of the SGR.

The burst has a duration (T90) of about 0.1 seconds and is best fit
by a power law function with an exponential high-energy cutoff.
The power law index is 0.54 +/- 0.07 and the cutoff energy,
parameterized as Epeak, is 36.1 +/- 0.3 keV.
The event fluence (10-1000 keV) from T0-0.064 to T0+0.128 is
(2.52 +/- 0.03)E-06 erg/cm^2, and the average photon flux
(10-1000 keV) over this time period is 289 +/- 3 ph/s/cm^2.

Fermi GBM also triggered on two other bursts from SGR 1935+2154.
The first occurred on 6 July 2021 at 03:50:09.75 UT
(trigger 647236214 / 210706160) and the second on 7 July 2021
at 15:45:11.08 UT (trigger 647365516 / 210707656).

Additionally, an automated, blind search for short gamma-ray bursts
below the onboard triggering threshold in Fermi-GBM identified a
potential burst from SGR 1935+2154. This event (trigger 647276517)
occurred on 6 July 2021 at 15:01:52.68 UT. It is approximately
0.1 s in duration and displays emission between 30-300 keV.
The burst localization is broadly consistent with the SGR position.

The spectral analysis results presented above are preliminary.
We encourage multi-wavelength observations to follow-up this most recent
activation.

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