MoCA: A Monte Carlo code for Comptonisation in Astrophysics I. Description of the code and first results

0500121 - ASÚ 2019 RIV FR eng J - Článek v odborném periodiku
Tamborra, Francesco - Matt, G. - Bianchi, S. - Dovčiak, Michal
MoCA: A Monte Carlo code for Comptonisation in Astrophysics I. Description of the code and first results.
Astronomy & Astrophysics. Roč. 619, November (2018), č. článku A105. ISSN 0004-6361. E-ISSN 1432-0746
GRANT EU: European Commission(XE) 312789 - STRONGGRAVITY
Institucionální podpora: RVO:67985815
Klíčová slova: polarization * accretion disks * active galaxies
Obor OECD: Astronomy (including astrophysics,space science)
Impakt faktor: 6.209, rok: 2018

We present a new Monte Carlo code for Comptonisation in Astrophysics (MoCA). To our knowledge MoCA is the first code that uses a single photon approach in a full special relativity scenario, and including also Klein-Nishina effects as well as polarisation. In this paper we describe in detail how the code works, and show first results from the case of extended coronae in accreting sources Comptonising the accretion disc thermal emission. We explored both a slab and a spherical geometry, to make comparison with public analytical codes more easy. Our spectra are in good agreement with those from analytical codes for low/moderate optical depths, but differ significantly, as expected, for optical depths larger than a few. Klein-Nishina effects become relevant above 100 keV depending on the optical thickness and thermal energy of the corona. We also calculated the polarisation properties for the two geometries, which show that X-ray polarimetry is a very useful tool to discriminate between them.
Trvalý link: http://hdl.handle.net/11104/0292260