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GCN Circular 22626

Subject
GRB 180409A: Fermi GBM observation
Date
2018-04-10T18:11:51Z (6 years ago)
From
Elisabetta Bissaldi at INFN,Bari <elisabetta.bissaldi@ba.infn.it>
E. Bissaldi (Politecnico & INFN Bari) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:


"At 08:18:18.67 UT on 9 April 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 180409A (trigger 544954703 / 180409346),
which was triangulated by IPN (Hurley et al., GCN 22619) and was also
detected by Konus (Frederiks et al., GCN 22621).

The on-ground calculated location, using the GBM trigger data, is

RA = 178.18, DEC = +36.050 (J2000 degrees),

with an uncertainty of 1 degree (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which we have characterized as a core-plus-tail model, with 90% of
GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg
systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ).

The angle from the Fermi LAT boresight at the GBM trigger time is 71 degrees.

The GBM light curve consists of multiple peaks
with a duration (T90) of about 13 s (50-300 keV).
The time-averaged spectrum from T0-0.5 s to T0+15 s is
best fit by a Band function with Epeak = 151 +/- 5 keV,
alpha = -0.85 +/- 0.03, and beta = -2.33 +/- 0.05.

The event fluence (10-1000 keV) in this time interval is
(2.87 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+10.1 s in the 10-1000 keV band
is 41 +/- 1 ph/s/cm^2.


The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
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