On the high energy cut-off of accreting sources: Is general relativity relevant?

0496101 - ASÚ 2019 RIV GB eng J - Journal Article
Tamborra, Francesco - Papadakis, I.E. - Dovčiak, Michal - Svoboda, Jiří
On the high energy cut-off of accreting sources: Is general relativity relevant?
Monthly Notices of the Royal Astronomical Society. Roč. 475, č. 2 (2018), s. 2045-2050. ISSN 0035-8711. E-ISSN 1365-2966
R&D Projects: GA ČR(CZ) GA17-02430S; GA MŠMT(CZ) LTAUSA17095
EU Projects: European Commission(XE) 312789 - STRONGGRAVITY
Institutional support: RVO:67985815
Keywords : black hole physics * relativistic processes * Seyfert galaxies
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 5.231, year: 2018

The hard X-ray emission observed in accreting compact sources is believed to be produced by inverse Compton scattering of soft photons arising from the accretion disc by energetic electrons thermally distributed above the disc, the so-called X-ray corona. Many independent observations suggest that such coronae should be compact and located very close to the black hole. In this case, general relativistic (GR) effects should play an important role to the continuum X-ray emission from these sources, and, in particular, in the observed high energy cut-off, which is a measure of the intrinsic temperature of the corona. Our results show that the energy shift between the observed and intrinsic high energy cut-off due to GR effects can be as large as two to eight times, depending on the geometry and size of the corona as well as its inclination. We provide estimates of this energy shift in the case of a lamp-post and a flat, rotating corona, around a Kerr and a Schwartzschild black hole, for various inclinations, and coronal sizes. These values could be useful to correct the observed high energy cut-off and/or coronal temperatures, either in the case of individual or large sample of objects.
Permanent Link: http://hdl.handle.net/11104/0288912