Volume 623, March 2019
|Number of page(s)||8|
|Published online||28 March 2019|
Nuclear γ-ray emission from very hot accretion flows
Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
2 Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, UK
3 National Research Nuclear University MEPhI, Kashirskoje Shosse, 31, 115409 Moscow, Russia
4 Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907-2036, USA
5 Astrophysical Big Bang Laboratory, RIKEN, 351-0198 Saitama, Japan
6 Space Research Institute of the Russian Academy of Sciences (IKI), 84/32 Profsoyuznaya Str, Moscow 117997, Russia
Accepted: 5 February 2019
Optically thin accretion plasmas can reach ion temperatures Ti ≥ 1010 K and thus trigger nuclear reactions. Using a large nuclear interactions network, we studied the radial evolution of the chemical composition of the accretion flow toward the black hole and computed the emissivity in nuclear γ-ray lines. In the advection dominated accretion flow (ADAF) regime, CNO and heavier nuclei are destroyed before reaching the last stable orbit. The overall luminosity in the de-excitation lines for a solar composition of plasma can be as high as few times 10−5 the accretion luminosity (Ṁc2) and can be increased for heavier compositions up to 10−3. The efficiency of transformation of the kinetic energy of the outflow into high energy (≥100 MeV) γ-rays through the production and decay of π0-mesons can be higher, up to 10−2 of the accretion luminosity. We show that in the ADAF model up to 15% of the mass of accretion matter can “evaporate” in the form of neutrons.
Key words: accretion, accretion disks / gamma rays: general / nuclear reactions, nucleosynthesis, abundances / stars: black holes
© E. Kafexhiu et al. 2019
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Open Access funding provided by Max Planck Society.
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