[vsnet-grb-info 25487] GRB 200415A: Fermi GBM observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  27587
SUBJECT: GRB 200415A: Fermi GBM observation
DATE:    20/04/15 19:54:14 GMT
FROM:    Elisabetta Bissaldi at INFN,Bari  <elisabetta.bissaldi at ba.infn.it>

E. Bissaldi (Politecnico and INFN Bari), M. Briggs (UAH),
E. Burns (GSFC), O.J. Roberts (USRA) and P. Veres (UAH)
report on behalf of the Fermi GBM Team:


"At 08:48:05.56 UT on 15 April 2020, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 200415A (trigger 608633290 / 200415367),
which was also detected by Fermi-LAT (Omodei et al., GCN 27586).
The Fermi GBM Final Real-time Localization (GCN 27579)
is consistent with the LAT position.

The angle from the Fermi LAT boresight
at the GBM trigger time is 49 degrees.

The GBM light curve shows a bright single pulse
with a duration (T90) of about 0.2 s (50-300 keV).
The time-averaged spectrum from T0-0.032 s to T0+0.160 s is
adequately fit by a power law function with an exponential
high-energy cutoff. The power law index is 0.07 +/- 0.05 and
the cutoff energy, parameterized as Epeak, is 950 +/- 40 keV.

The event fluence (10-1000 keV) in this time interval
is (5.2 +/- 0.1)E-06 erg/cm^2. The 64-ms peak photon flux
measured starting from T0 in the 10-1000 keV band
is 74 +/- 2 ph/s/cm^2.

While we report the source to be a possible short GRB,
we cannot conclusively rule out a giant magnetar flare
of extragalactic origin, as reported by IPN (GCN 27585).
Periodicity is not evident in the GBM data.
Assuming a distance of 3.5 Mpc and the spectral shape reported above,
the isotropic equivalent energy in the 1 keV-10 MeV range is
(1.22 +/- 0.03)E+46 erg. Further analysis is ongoing.


The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

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