Research Note

Is the energy generation rate of nuclear reactions in hot accretion flows important?

¹ Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatories, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, China e-mail: [hzhang;fyuan]@shao.ac.cn
² Graduate School of the Chinese Academy of Sciences, Beijing 100039, PR China
³ University of Science and Technology of China, Hefei, Anhui 230026, PR China e-mail: ywa@mail.ustc.edu.cn
⁴ Department of Astronomy, Nanjing University, Nanjing 210093, PR China
⁵ The Open Laboratory of Cosmic Ray and High Energy Astrophysics, Chinese Academy of Sciences, Beijing 100049, PR China

Received: 8 March 2009
Accepted: 13 May 2009

Abstract

The temperature of hot accretion flows around black holes is sufficiently high for the ignition of nuclear reactions. This is potentially an important nucleosynthesis mechanism in the universe. As the first step in studying this problem, we need to measure physical quantities such as density and temperature of the accretion flow. In usual studies of the hot accretion flow, viscous dissipation is considered to be the only heating mechanism, while the heating caused by nuclear reactions is not considered. In this paper, we investigate whether the energy generation rate of nuclear reaction is important compared to the viscous heating. Our calculation indicates that the former is at most one percent of the latter and thus is not important. The dynamics of accretion flow can be therefore calculated in the usual way, without the need to consider heating due to nuclear reactions.