title: Nonthermal Processes Near Supermassive Black Holes
creator: Katsoulakos, Grigorios
subject: ddc-520
subject: 520 Astronomy and allied sciences
subject: ddc-530
subject: 530 Physics
description: 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.
date: 2019
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/27354/1/PhD_Thesis.pdf
identifier: DOI:10.11588/heidok.00027354
identifier: urn:nbn:de:bsz:16-heidok-273545
identifier:   Katsoulakos, Grigorios  (2019) Nonthermal Processes Near Supermassive Black Holes.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/27354/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng