GCN Circular 23712

A. Ursi (INAF/IAPS), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), M.
Marisaldi (INAF/OAS-Bologna, and Bergen University), N. Parmiggiani
(INAF/OAS-Bologna), F. Longo (Univ. Trieste and INFN Trieste), A. Argan, M.
Cardillo, C. Casentini, Y. Evangelista, G. Piano (INAF/IAPS), F. Lucarelli,
C. Pittori, F. Verrecchia (SSDC, and INAF/OAR), A. Bulgarelli, V. Fioretti,
F. Fuschino (INAF/OAS-Bologna), M. Pilia, A. Trois (INAF/OA-Cagliari), I.
Donnarumma (ASI), A. Giuliani (INAF/IASF-Mi), report on behalf of the AGILE
Team:

The AGILE Mini-CALorimeter (MCAL) detected the GRB 190114C at T0 =
2019-01-14 20:57:02.26 +/- 0.01 s (UTC), which was also detected by
Swift/BAT-XRT (Gropp et al., GCN #23688), MASTER (Tyurina et al., GCN
#23690), Pan-STARRS (de Ugarte Postigo et al., GCN #23692), NOT (Selsing et
al., GCN #23695), OASDG (Izzo et al., GCN #23699), GROND (Bolmer et al.,
GCN #23702), Fermi/GBM (Hamburg et al., GCN #23707), Fermi/LAT (Kocevski et
al., GCN #23709), X-shooter (Kann et al., GCN #23710), and representing the
first GRB ever detected by ground-based Cherenkov telescopes (MAGIC,
Mirzoyan et al., GCN #23701).

In the 0.4-100 MeV energy band, the event lasted T90=6.2 s and released a
total number of ~32600 counts in the detector, above an average background
rate of about 700 Hz. The light curve shows several peaks, which can be
grouped in three episodes, characterized by different energy profiles: the
first and third episodes are mostly constituted of counts with energies <
1.4 MeV, whereas the second central episode exhibits a substantial fraction
of high-energy counts with energies > 1.4 MeV. The AGILE/MCAL light curve
can be viewed at:
http://www.agilescienceapp.it/results/wp-content/uploads/2019/01/GRB190114C_MCAL-1.png
.

The time-integrated spectrum of the first episode (from T0 to T0+2.5 s) can
be fitted in the energy range [0.4-2 MeV] with a simple power law with
ph.ind.=2.55 -0.07/+0.08, resulting in a reduced chi-square of 1.56 (21
d.o.f.). The burst fluence in the same energy range and time interval is
2.11e-05 erg/cm^2 (90% confidence level).

The time-integrated spectrum of the second episode (from T0+2.5 s to T0+4.8
s) can be fitted in the energy range [0.4-60 MeV] with a broken power law
with alpha=1.46 -0.35/+0.41, beta=2.53 -0.05/+0.07, and a break energy of
750 +56/-110 keV, resulting in a reduced chi-square of 1.44 (46 d.o.f.).
This episode is possibly made by several spectral components. The burst
fluence in the same energy range and time interval is 1.31e-4 erg/cm^2 (90%
confidence level).

The time-integrated spectrum of the third episode (from T0+4.8 s to T0+6.2
s) can be fitted in the energy range [0.4-2 MeV] with a simple power law
with ph.ind.=2.95 -0.09/+0.10, resulting in a reduced chi-square of 1.11
(21 d.o.f.). The burst fluence in the same energy range and time interval
is 1.11e-05 erg/cm^2 (90% confidence level).

The GRB is clearly detected also by the AGILE scientific ratemeters: in
particular, by the Super-AGILE (20-60 keV), Anti-Coincidence (50-200 keV),
and MCAL (0.4-100 MeV) ratemeters.

Further analysis is still in progress.

The AGILE-MCAL detector has a full solid angle acceptance, and is
operational in the range 0.4 - 100 MeV.