Modeling High-Resolution Spectra from X-ray Illuminated Accretion Disks

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Modeling High-Resolution Spectra from X-ray Illuminated Accretion Disks

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dc.contributor.advisor Kraemer, Steven en_US Garcia, Javier A. en_US
dc.contributor.other Bruhweiler, Frederick en_US 2012-04-02T15:43:33Z 2012-04-02T15:43:33Z 2010 en_US 2012-04-02T15:43:33Z
dc.identifier.other Garcia_cua_0043A_10151 en_US
dc.description Degree awarded: Ph.D. Physics. The Catholic University of America en_US
dc.description.abstract This work focuses on the study of X-ray illuminated accretion disks aroundblack holes by modeling their structure and reprocessed emission. The calculationof new models for the reflected spectra consider the effects of incident X-rays on thesurface of an accretion disk by solving simultaneously the equations of radiativetransfer, energy balance and ionization equilibrium over a large range ofcolumn densities. Plane-parallel geometry and azimuthal symmetry are assumed,such that each calculation corresponds to a ring at a given distance from the centralobject. The radiation transfer equations are solved by using the Feautrier scheme.Ionization and thermal balance are solved by using the photoionization code XSTAR,including the most recent and complete atomic data for K-shell of the isonuclearsequences of iron, oxygen, and nitrogen. The redistribution of photons due to Comptonscattering is included using a Gaussian approximation for the Compton kernel.The atomic data for nitrogen ions, namely, level energies, wavelengths,gf-values, radiative widths, total and partial Auger widths, and total and partialphotoionization cross sections are computed with a portfolio of publicly availableatomic physics codes: AUTOSTRUCTURE, HFR, and BPRM.The shape of the Fe K-line is perhaps one of the most important features inthe X-ray spectrum of accreting sources. Therefore, the effect of fluorescentK&alpha line emission and absorption in the emitted spectrumis explored, as well as the dependence of the spectrum on the strength of the incidentX-rays and other input parameters and the importance of Comptonization on the emittedspectrum. These calculations predict under which conditionsthe line is formed, providing information about the ionization stage of the emitting gas.The width of this line is often related to relativistic effects (i.e. gravitational redshift),since the emitting gas may be located in regions close to the black hole. However, thesemodels suggest that the energy redistribution of the photons due to Compton scatteringalso affects the line profile and it is responsible for an important fraction of thebroadening. en_US
dc.format.extent 180 p. en_US
dc.format.mimetype application/pdf en_US
dc.publisher The Catholic University of America en_US
dc.subject Astrophysics en_US
dc.subject Physics, Astronomy and Astrophysics en_US
dc.subject Physics, Atomic en_US
dc.subject.other accretion: accretion disks en_US
dc.subject.other atomic processes en_US
dc.subject.other black hole physics en_US
dc.subject.other line: formation en_US
dc.subject.other radiative transfer en_US
dc.subject.other X-rays: general en_US
dc.title Modeling High-Resolution Spectra from X-ray Illuminated Accretion Disks en_US
dc.type Text en_US
dc.type Dissertation en_US

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