GCN Circular 30831
Subject
Fermi GBM observation of another bright burst in the direction of SGR 1935+2154
Date
2021-09-13T03:33:14Z (4 years ago)
From
Oliver J Roberts at USRA/NASA <oliver.roberts@nasa.gov>
O.J. Roberts (USRA/NASA-MSFC) reports on behalf of the Fermi GBM Team:
"At 20:16:10.44 UT on 12 September 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 653170575/210912845).
The GBM on-ground location is consistent with the known position of the SGR.
The angle from the Fermi LAT boresight at the GBM trigger time is 96 degrees.
The event episode has a duration (T90) of about 1 s (10-1000 keV). During this
time interval, there are several very short bursts. The first burst has a
rapid risetime.
The whole event is best fit with a power law function
with an exponential high-energy cutoff. The power law index is 0.08 +/- 0.08 and
the cutoff energy, parameterized as Epeak, is 32.1 +/- 0.3 keV.
The time-integrated event fluence (10-1000 keV) from T0-0.064 to T0+0.944s is
(3.545 +/- 0.038)E-6 erg/cm^2. The average photon flux in the
10-1000 keV band during this period is 84 +/- 1 ph/s/cm^2.
Fermi GBM has also triggered on a further 24 bursts from the direction of SGR 1935+2154
since yesterday's GCN (Roberts and Wood, GCN 30806):
Date and Time in UTC Fermi MET (s)
2021-09-12T23:19:32.08 653181577
2021-09-12T20:16:10.44 653170575
2021-09-12T15:03:50.60 653151835
2021-09-12T13:55:16.45 653147721
2021-09-12T12:19:20.44 653141965
2021-09-12T10:10:11.73 653134216
2021-09-12T07:28:07.46 653124492
2021-09-12T06:51:13.22 653122278
2021-09-12T05:14:07.84 653116452
2021-09-11T02:36:38.24 653093506
2021-09-11T20:22:59.04 653084584
2021-09-11T20:05:46.22 653083551
2021-09-11T18:54:36.05 653079281
2021-09-11T17:01:09.77 653072474
2021-09-11T16:50:03.83 653071808
2021-09-11T16:36:57.91 653071022
2021-09-11T15:26:11.55 653066776
2021-09-11T15:15:25.44 653066130
2021-09-11T15:03:00.55 653065385
2021-09-11T13:27:33.85 653059658
2021-09-11T11:53:57.29 653054042
2021-09-11T10:42:51.85 653049776
2021-09-11T05:32:38.65 653031163
2021-09-11T03:02:28.36 653022153
Fermi GBM will not report on future triggers from this event.
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/"