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キーワード:
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要旨:
In recent years, γ-ray astronomy has made considerable progress in the exploration
of the extragalactic γ-ray sky. In particular, active galaxies, whose
relativistic jets/outflows are significantly inclined with respect to the lineof-
sight, have revealed remarkable flaring activity at γ-ray energies. The
observed rapid variability of the γ-ray emission, comparable to timescales of
the light travel time across the black hole horizon, provides a strong motivation
for testing radiative scenarios associated with the vicinity of the central
supermassive black hole. In this doctoral study, we explore the so-called
black hole magnetospheric scenario. Accordingly, strong particle acceleration
may occur within the black hole magnetosphere in regions of unscreened
electric fields (gaps). This can happen either at the null surface across which
the charge density changes sign or at the stagnation surface which separates
the inwardly from the outwardly moving matter. The acceleration of leptons
is accompanied by γ-ray emission via inverse Compton scattering of the ambient
(disk) soft photons as well as curvature radiation. This thesis explores
the potential of these processes to account for the observed γ-ray features.
By developing and studying an one-dimensional, steady model for magnetospheric
particle acceleration and emission, as well as, estimating the terminal
Lorentz factors of the accelerated charges and the maximum extractable gap
power, we find that magnetospheric processes can be responsible for the observed,
rapidly variable very-high-energy γ-ray emission in the radio galaxy
M87.
