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Modélisation de l'émission X et Gamma des objets compacts par les méthodes Monte-Carlo

Abstract : The study of high energy radiative processes in relativistic plasma surrounding compact objects requires advanced simulation tools. I present numerical codes designed to simulate these processes (multiple Compton scatering, pair annihilation and production, Fe fluorescence...). First, standard linear Monte-Carlo codes are useful to compute the spectra arising from Comptonisation process or reflection on cold matter. Theses calculations are performed assuming a specific plasma geometry and particle distribution. Second, a non-linear Monte-Carlo code has been developed. This method enable to avoid assumptions on the electron (or pair) distribution which is computed self-consistently according to energy and pair balance and taking into account the radiative coupling with the cold matter present in the vicinity of the active region. The free parameters are then the power injected in the plasma and the way it is provided (thermal heating or injection/acceleration of high energy particles). The computed spectra when compared to observations, give the information on the steady-state particle energy distribution and the energy dissipation processes. In addition, this code can also deal with time dependent nonon-equilibrium situations. It enable to compute the evolution of the physical parameters as well as the light curves in different energy bands as a response to a varying plasma heating or soft photon input. Application to several model proposed to explain the X and gamma-ray observations are presented (thermal and non-thermal models, anisotropic illumination model and accretion disk coronna models). I show how such numerical tools can be used to put constraints on the geometry and physical parameters of the X-ray and gamma-ray emitting region of compact sources.
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https://tel.archives-ouvertes.fr/tel-00010420
Contributor : Julien Malzac <>
Submitted on : Friday, October 7, 2005 - 7:26:15 PM
Last modification on : Monday, April 5, 2021 - 2:26:07 PM
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Julien Malzac. Modélisation de l'émission X et Gamma des objets compacts par les méthodes Monte-Carlo. Astrophysique [astro-ph]. Université Paul Sabatier - Toulouse III, 1999. Français. ⟨tel-00010420⟩

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