Fermi GBM Observations of SGR J1935+2154

ATel #14764; R. Hamburg (UAH), C. Malacaria (USRA), and C. Fletcher (USRA)
on 7 Jul 2021; 17:38 UT
Credential Certification: Oliver Roberts (oliver.roberts@nasa.gov)

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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/"

official Fermi GBM Support Page