Nuclear γ-ray emission from very hot accretion flows
Abstract
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.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- March 2019
- DOI:
- 10.1051/0004-6361/201833948
- arXiv:
- arXiv:1807.09507
- Bibcode:
- 2019A&A...623A.174K
- Keywords:
-
- accretion;
- accretion disks;
- gamma rays: general;
- nuclear reactions;
- nucleosynthesis;
- abundances;
- stars: black holes;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 7 pages, 7 figures