[vsnet-grb-info 16215] Fermi GBM Observations of SGR 1935+2154

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17496
SUBJECT: Fermi GBM Observations of SGR 1935+2154
DATE:    15/02/23 08:28:08 GMT
FROM:    Eric Burns at U of Alabama  <eb0016 at uah.edu>

E. Burns (UAH) and G. Younes (GWU)
report on behalf of the Fermi GBM Team:

"At 17:57:05.99 UT on 23 February 2015, the Fermi Gamma-Ray Burst
Monitor triggered (446320628/150222748) on a burst from
SGR 1935+2154, which was reported to be in outburst by
Burrows et al. (GCN 17485). The GBM burst occurred over 5 hours
after the bursts detected by the Swift BAT. The GBM on-ground
location is consistent with the known source position.

The burst consists of a single pulse, with a duration of
about 0.05 s. The burst is well-fit with a power law function
with an exponential high-energy cutoff parameterized as
Epeak = 29 +/- 1 keV and an Index -0.25 +/- 0.31. The corresponding
peak flux integrated over 16ms (10-1000 keV) is
(146 +/- 8)E-06 erg/s/cm^2. The fluence during T0-0.048s to
T0+0.000s is (1.6 +/- 0.1)E-07 erg/cm^2. A fit to a double
black-body spectrum is a statistical tie with the exponential
power-law fit, with one extra parameter and blackbody temperatures
of 4.3 +/- 0.7 keV and 10.4 +/- 1.0 keV. The other models reported
in Krimm et al. (GCN 17490) are not statistically favored.

This burst was followed by four further triggers at
19:44:16.94 UT (trigger 446327059/150222822) on 22 February 2015,
01:38:07.99 UT (446348290/150223068),
05:24:54.16 UT (446361897/150223226), and
06:45:40.13 UT (446366743/150223282) on 23 February 2015,
all consistent with being from SGR 1935+2154.
All of these triggers consist of a single peak. The third trigger,
150223068, is several times more intense than the others, which are
of about equal intensity.

The analysis results presented above are preliminary.

These bursts are bright enough that some are being classified by
the flight software as GRBs. We will correct this classification
in the online catalog at the Fermi Science Support Center:

http://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigtrig.html

but will not issue further circulars to correct the classification."