Nucleosynthesis in accretion flows around Black Holes

TL;DR

This paper investigates nucleosynthesis in accretion flows around black holes, highlighting how different flow conditions influence chemical composition changes and potential energetic and stability effects.

Contribution

It provides detailed modeling of composition changes in accretion flows using an extensive nuclear network, revealing conditions under which significant nucleosynthesis occurs.

Findings

Significant nucleosynthesis occurs in low-viscosity, low-accretion-rate flows.

Composition changes may influence galactic metallicities.

Energy variations could induce instabilities and oscillations in accretion flows.

Abstract

Significant nucleosynthesis is possible in the centrifugal pressure-supported dense and hot region of the accretion flows which deviate from Keplerian disks around black holes. We compute composition changes and energy generations due to such nuclear processes. We use a network containing 255 species and follow the changes in composition. Highly viscous, high-accretion-rate flows deviate from a Keplerian disk very close to the black hole and the temperature of the flow is very small due to Compton cooling. No significant nucleosynthesis takes place in these cases. Low-viscosity and lower-accretion-rate hot flows deviate farther out and significant changes in composition are possible in these cases. We suggest that such changes in composition could be contributing to the metallicities of the galaxies. Moreover, the radial variation of the energy generation/absorption specifically due to proton capture and photo-dissociation reactions could cause instabilities in the inner regions of the accretion flows. For most of these cases sonic point oscillations may take place. We discuss the possibility of neutrino emissions.