NUCLEAR REACTIONS IN HOT ASTROPHYSICAL PLASMAS WITH T > 10¹⁰ K

Abstract

The importance of nuclear reactions in low-density astrophysical plasmas with ion temperatures T ≥1010 K has been recognized for more than thirty years. However, the lack of comprehensive data banks of relevant nuclear reactions and the limited computational power have not previously allowed detailed theoretical studies. Recent developments in these areas make it timely to conduct comprehensive studies on the nuclear properties of very hot plasmas formed around compact relativistic objects such as black holes and neutron stars. Such studies are of great interest in the context of scientific programs of future low-energy cosmic γ-ray spectrometry. In this work, using the publicly available code TALYS, we have built a large nuclear network relevant for temperatures exceeding 1010 K. We have studied the evolution of the chemical composition and accompanying prompt gamma-ray emission of such high-temperature plasmas. We present the results on the abundances of light elements D, T, 3 He , 4 He , 6 Li , 7 Li , 9 Be , 10 B , 11 B , and briefly discuss their implications on the astrophysical abundances of these elements.

Nucleosynthesis of elements in gamma-ray burst engines

“…The network is working well for the temperature ranges about or below 1 MeV, and our method is appropriate for the outer parts of accretion disks in GRBs. For hotter astrophysical plasmas, more advanced computations could be appropriate (Kafexhiu et al 2012).…”

Gamma-ray emission of hot astrophysical plasma

“…From Eq. (2), calculation of the σ v l ij requires the reaction cross section σ l ij that we obtain either directly from the experimental data or calculate it using the modern nuclear code TALYS [20] that provides a complete description of all reaction channels and uses many state-of-the-art nuclear models, for more details see [17]. We note that the recent version of the code TALYS can calculate cross sections for energies The cyan dash-dot-line shows the thermal electron bremsstrahlung at kTe = 100 keV (typical for two temperature accretion models).…”

“…In low-density plasma, the processes are dominated by binary interactions. We use the methods developed for calculations of the nuclear cross-section [17] as well as the parametrisations of π 0 -meson production cross sections with particular attention to the energy region close to the kinematic threshold [18].…”

Nuclear γ-ray emission from very hot accretion flows

“…This system forms a so-called nuclear reaction network. For calculating the cross sections σ l i j we use the nuclear code TALYS (Koning et al 2005) and experimental data, for more details see Kafexhiu et al (2012). We note that the recent version of the code TALYS can calculate cross sections for energies up to 1 GeV.…”

“…Nuclear reactions play an important role in such high ion temperature accretion plasmas. These reactions change the plasma chemical composition and produce a characteristic γray emission, (Aharonian & Sunyaev 1984;Aharonian & Syunyaev 1987;Yi & Narayan 1997;Kafexhiu et al 2012). Because of the high ion temperature, the nuclear spallation processes dominate.…”