Screening effect on electron capture in presupernova stars

Abstract

Aims. With the new electron capture results from the improved GT resonance distribution, we analyzed the electron screening effect on electron capture at the presupernova stage. Methods. The relativistically degenerate electron liquid screening potential derived from the linear response theory are adopted. The calculation of the electron capture rates is based on the shell-model. Both the change of electron energy and the shift in the threshold for electron capture in screening are taken into account. Results. The results indicate that the influence of electron screening on the electron capture is prominent in high-density matter. As the improved electron capture rate is considered, screening effect on the electron capture rate increases by about 1 percent at ρY e > 10 9 g/cm 3 . Conclusions. The influence of screening on the electron capture reaction is about 10 percent for 56 Co at ρY e ≈ 10 9 g/cm 3 . Screening may affect the structure and evolution of presupernova and should be included in any precise simulation.

Dynamical screening effects on big bang nucleosynthesis

“…In the early phase, BBN condition maintains enough high temperature to allow the nuclear statistical equilibrium (NSE). The NSE continues to increase 4 He up to T = 0.6 MeV, where the relatively slow increase of 3 H and 3 He slows down the reaction rate of 3 H(p, γ) 4 He and 3 He(n, γ) 4 He. By JCAP11(2021)017 the slow production rate, 4 He is decoupled from NSE and follows the NSE curve of 3 H and 3 He.…”

“…In the dielectric function (equation (2.2)), the third and fourth terms result from the contributions by the 1 H and 4 He. Here we neglect contributions of other nuclei such as D, 3 He, 7 Li, and 7 Be due to their small numbers. For each species, we use the Debye radius and thermal velocity as λ D,i = T /(4πn i Z 2 i e 2 ) and v T,i = (T /m i ) 1/2 , respectively.…”

“…depending on the temperature and the electron number density n e . Since the screening effects change the thermonuclear reaction rates, the Salpeter form has been exploited widely in nucleosynthesis such as the stellar nuclear fusion [2], presupernova (preSN) [3], and core-collapsing supernova [4]. Among various studies, in particular, big bang nucleosynthesis (BBN) has been a good testbed for the screening effects owing to a relatively small number of main reactions and precise observational data based on cosmic microwave background (CMB) study and astronomical spectroscopy.…”

Effect of electron screening on the collapsing process of core-collapse supernovae

“…Screening reduces the energy of the electron and enhances the threshold energy, so the EC rate will decrease. We adopt the method similar to Liu et al (2007), i.e., we ignore the effect screening changes the Coulomb in-wave function of the electron, only consider the effect on the electron energy and threshold energy. So the capture rate in the strong screening is rewritten as…”

“…Their results show screening can reduce the EC rate by 10–20 per cent at high density. More recently improved EC rate and screening potential were adopted in Liu, Zhang & Luo (2007). The screening affects the EC mainly in three aspects.…”