[vsnet-grb-info 27271] Fermi GBM Observations of SGR J1935+2154

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29374
SUBJECT: Fermi GBM Observations of SGR J1935+2154
DATE:    21/01/29 23:56:51 GMT
FROM:    Oliver J Roberts at USRA/NASA  <oliver.roberts at nasa.gov>

O.J. Roberts (USRA), J. Wood (USRA), A. von Kienlin (MPE), P. Veres (UAH)
and G. Younes (GWU) report on behalf of the Fermi GBM Team:

"At 15:23:29.92 UT on January 29th 2020, the Fermi Gamma-Ray Burst 
Monitor (GBM) triggered and located a burst from SGR 1935+2154 
(trigger 633626614 / 210129641). SGR J1935 bursts have also been reported 
by Konus-Wind (Ridnaia et al., GCN 29373), GECAM (Y. Huang et al., GCN 29363) 
and Swift-BAT (Ridania et al., GCN 29365).

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. There are two additional bursts
that also appear to be from SGR J1935, about 354s after the trigger time.

It is adequately fit by a power law function with an exponential high-energy cutoff. 
The power law index is 0.2 (+0.2/-0.2) and the cutoff energy, parameterized as 
Epeak, is 32.9 (+0.6/-0.6) keV.

The event fluence (10-1000 keV) from T0-0.064s to T0+0.064s 
is (5.2 +/- 0.1)E-7 erg/cm^2. The average photon flux in the 10-1000 keV band during 
this period is 94.6 +/- 1.9 ph/s/cm^2.

The spectrum is also well fit using a double blackbody (BB+BB) fit, with low and high 
temperatures of 6.2 (+0.6/-0.7) and 12.5 (+1.6/-1.3) keV, respectively.

Fermi GBM also subsequently triggered on multiple bursts from SGR J1935+2154 on 
January 24th, 28th and today, with a fraction of these being misclassified as GRBs. 
These triggers are:

January 29th:
210129886 / 633647760    (21:15:55.98 UTC)
210129441 / 633609344    (10:35:39.94 UTC)
210129116 / 633581187    (02:46:22.58 UTC)

January 28th
210128983 / 633569707    (23:35:02.48 UTC)

January 24th
210124867 / 633214108    (20:48:24.00 UTC)
210124325 / 633167319    (07:48:34.36 UTC)

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/”