Resonant nuclear reaction ${}^{23}$Mg $(p,\gamma )$ ${}^{24}$Al in strongly screening magnetized neutron star crust

Abstract

Basing on the relativistic theory in superstrong magnetic fields (SMFs), we investigate the influence of strong electron screening (SES) on the rates of nuclear reaction ${}^{23}$Mg $(p,\gamma )$ ${}^{24}$Al by three models of Lai (LD), Fushiki et al. (FGP), and Liu et al. (LJ) on the surface of magnetars. Our results show that the rates can be greatly enhanced by three orders of magnitude due to the influence of SES. The rates in our model are in good agreement with those of LD and FGP at relatively low density environment (e.g. ${\rho }_7<0.01$) for $1<B_{12}<10^2$. On the other hand, in relatively high magnetic fields (e.g. $B_{12}>10^2$), the rates of our model can be 1.58 times and around three orders of magnitude larger than those of FGP and LD, respectively. The significant increase of the rates of our model for ${}^{23}$Mg $(p,\gamma )$ ${}^{24}$Al implies that more ${}^{23}$Mg will escape from the Ne-Na cycle due to SES in SMFs. As a consequence, the next reaction ${}^{24}$Al $({\beta }^{+},\nu )$ ${}^{24}$Mg will produce more ${}^{24}$Mg to participate in the Mg-Al cycle. Thus, it may lead to synthesize a large amount of production of $A\ge 20$ nuclides (e.g. ${}^{26}$Al) on the surface of magnetars. These heavy elements (e.g. ${}^{26}$Al) may be thrown out due to the compact binary mergers of double neutron star (NS-NS) or black hole and neutron star (BH and NS) systems. Our results may help to understand why the ${}^{26}$Al is always overabundance in the interstellar space. Our conclusion may be helpful to the investigation of the nucleosynthesis of some heavy elements, the energy generation rate, and the numerical calculations of magnetars evolution.

Comments: 44 pages, 6 figures, Accepted for publication in Chinese Physics C