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GCN Circular 23707

Subject
GRB 190114C: Fermi GBM detection
Date
2019-01-15T05:59:42Z (5 years ago)
From
Rachel Hamburg at UAH <rkh0007@uah.edu>
R. Hamburg (UAH), P. Veres (UAH), C. Meegan (UAH), E. Burns (GSFC),
V. Connaughton (USRA), A. Goldstein (USRA), D. Kocevski, and O.J. Roberts
(USRA)
report on behalf of the Fermi GBM Team:

"At 20:57:02.63 UT on 14 January 2019, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 190114C (trigger 569192227 / 190114873)
which was also detected by the Swift/BAT (Gropp et al. 2019, GCN 23688),
MASTER (Tyurina et al. 2019, GCN 23690; Lipunov et al. 2019, GCN 23693),
Pan-STARRS (de Ugarte Postigo et al. 2019, GCN 23692), NOT
(Selsing et al. 2019, GCN 23695), OASDG (Izzo et al. 2019, GCN 23699),
and GROND (Bolmer et al. 2019, GCN 23702) optical telescopes, and at
Very High Energy (VHE) by the MAGIC telescope (Mirzoyan et al. 2019,
GCN 23701). The GBM on-ground location is consistent with the Swift/BAT
position.

The angle from the Fermi LAT boresight at the GBM trigger time is 68
degrees.

The GBM light curve shows a very bright, multi-peaked pulse starting from
about T0+0 s to T0+15 s and is followed by a weaker pulse occurring at
approximately T0+15 s to T0+25 s. There is also evidence of fainter
emission
lasting to about T0+200 s. The calculated duration (T90) is about
116 s (50-300 keV). The time-averaged spectrum from T0-0.00 s to
T0+38.59 s can be fit by a Band function with Epeak = 998.6 +/- 11.9 keV,
alpha = -1.058 +/- 0.003, and beta = -3.18 +/- 0.07. The event fluence
(10-1000 keV) in this time interval is (3.99E-04 +/- 8.10E-07) erg/cm^2.
The 1-sec peak photon flux measured starting from T0+3.84 s in the 10-1000
keV band is 246.86 +/- 0.86 ph/s/cm^2.

Using the Band spectral fit and the distance measure of
z = 0.42 (Selsing et al. 2019), we calculate the energetics of GRB 190114C.
We estimate that the isotropic energy release in gamma-rays Eiso = 3E53
erg,
and the isotropic peak luminosity Liso = 1E53 erg/s,
in the 1 keV ��� 10 MeV energy band.

Preliminary spectral analysis shows a strong statistical preference for an
extra power-law component, previously seen in some bright bursts.
The TeV observations by MAGIC and the optical polarization observations by
MASTER begin at about T0+50 s. This is well after the main peaks observed
in GBM, but significant GBM emission is evident out to about 200 s,
covering
the start of these observations.

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