TITLE:   GCN CIRCULAR
NUMBER:  26689
SUBJECT: GRB 200109A: Fermi GBM observation
DATE:    20/01/09 19:22:09 GMT
FROM:    Rachel Hamburg at UAH  <rkh0007@uah.edu>

R. Hamburg (UAH) and C. Meegan (UAH) report on behalf of the Fermi GBM Team:

"At 01:45:51.89 UT on 9 January 2020, the Fermi Gamma-Ray Burst Monitor
(GBM) triggered and located GRB 200109A (trigger 600227156 / 200109074),
which also triggered the Swift/BAT approximately 25 s later
(Melandri et al. 2019, GCN 26678). The Fermi GBM Final Real-time
Localization (GCN 26677) is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 57
degrees.

The GBM light curve shows a complex structure with a duration (T90) of
about 41 s (50-300 keV). The time-averaged spectrum from T0-0.8 s to
T0+41.2 s is best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.98 +/- 0.08 and the
cutoff energy, parameterized as Epeak, is 449 +/- 109 keV.

The event fluence (10-1000 keV) in this time interval is
(6.9 +/- 0.6)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-0.7 s in the 10-1000 keV band
is 2.3 +/- 0.2 ph/s/cm^2.

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/"