eprintid: 2482
rev_number: 8
eprint_status: archive
userid: 1
dir: disk0/00/00/24/82
datestamp: 2002-07-24 00:00:00
lastmod: 2014-04-03 12:03:42
status_changed: 2012-08-14 15:05:01
type: doctoralThesis
metadata_visibility: show
creators_name: Gracia Calvo, Juan Jose
title: Time-dependent Accretion Flows onto Black Holes
title_de: Zeitabhängige Akkretionsflüsse auf Schwarze Löcher
ispublished: pub
subjects: ddc-530
divisions: i-714300
adv_faculty: af-13
keywords: Astrophysics , Hydrodynamics , Akkretion , Black Hole , Radiative Transfer
cterms_swd: Astrophysik
cterms_swd: Hydrodynamik
cterms_swd: Akkretion
cterms_swd: Schwarzes Loch
cterms_swd: Strahlungstransport
abstract_translated_text: Accretion onto compact objects plays a fundamental role in a number of astrophysical systems like active galactic nuclei (AGN) and black hole X-ray binaries (BHXB).  The standard thin disk model fails to reproduce the spectra of these systems.  They exhibit a blackbody-like component, generally attributed to the cold standard disk, and a hard power law-like component extending to several 100 keV, which cannot be accounted for by  the standard disk.  This situation can be remedied by assuming that the  accretion flow consists not only of the cold standard disk, but also of  a hot optically thin plasma in the immediate vicinity. This hot flow cools through advection rather than through radiation. This work addresses the question whether an inner hot optically thin disk can be self-consistently connected to an outer cold standard disk.  We come to the conclusion that radial transitions between the two flow types are in principle possible for a wide range of transition radii, which depend on the flow parameters. But while the flow evolves in time, the transition radius drifts radially outward until this reaches its outermost allowed location, which is in agrement with previous steady models. A second major result is, that the transition region is highly unstable. Oscillating modes of the Rayleigh-instability leak into the inner hot flow and make its hydrodynamical and spectral properties highly variable. The characteristic frequency of the oscillations is near to the local keplerian orbital frequency, which makes them a potential candidate for the high-frequency quasi-periodic oscillations present in the X-ray light-curves of BHXB's.
abstract_translated_lang: eng
class_scheme: pacs
class_labels: 97.10.Gz 0
date: 2002
date_type: published
id_scheme: DOI
id_number: 10.11588/heidok.00002482
portal_cluster_id: p-zah
portal_order: 02482
ppn_swb: 1643332147
own_urn: urn:nbn:de:bsz:16-opus-24829
date_accepted: 2002-07-17
advisor: HASH(0x55a9a633bd48)
language: eng
bibsort: GRACIACALVTIMEDEPEND2002
full_text_status: public
citation:   Gracia Calvo, Juan Jose  (2002) Time-dependent Accretion Flows onto Black Holes.  [Dissertation]     
document_url: https://archiv.ub.uni-heidelberg.de/volltextserver/2482/1/thesis.pdf