Nuclear $\gamma$-ray emission from very hot accretion flows

Abstract

Optically thin accretion plasmas can reach ion temperatures $T_{\mathrm{i}}\ge 10^{10}$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 $\gamma$-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 ($\dot{M}{c}^2$) 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 ($\ge 100$~MeV) $\gamma$-rays through the production and decay of ${\pi }^0$-mesons can be higher, up to $10^{-2}$ of the accretion luminosity. We show that in the ADAF model up to 15 percent of the mass of accretion matter can `evaporate' in the form of neutrons.

7 pages, 7 figures

References in corpus (4)

• The Primordial Lithium Problem
• Science with e-ASTROGAM (A space mission for MeV-GeV gamma-ray astrophysics)
• Neutron capture and 2.2 MeV emission in the atmosphere of the secondary of an X-ray binary
• Nuclear reactions in hot astrophysical plasmas with $T>10^{10}$ K

Cited by in corpus (3)

• Diffuse X-Ray and Gamma-Ray Limits on Boson Stars that Interact with Nuclei
• Line profile of nuclear de-excitation gamma-ray emission from very hot plasma
• Accelerated protons produced by magnetic Penrose process in Sgr A*