Neutrino signal from proto-neutron star evolution: Effects of opacities from charged-current–neutrino interactions and inverse neutron decay

Abstract

We investigate the impact of charged-current neutrino processes on the formation and evolution of neutrino spectra during the deleptonization of proto-neutron stars. To this end we develop the full kinematics of these reaction rates consistent with the nuclear equation of state, including weak magnetism contributions. This allows us to systematically study the impact of inelastic contributions and weak magnetism on the νe andνe luminosities and average energies. Furthermore, we explore the role of the inverse neutron decay, also known as the direct Urca process, on the emitted spectra ofνe. This process is commonly considered in the cooling scenario of cold neutron stars but has so far been neglected in the evolution of hot proto-neutron stars. We find that the inverse neutron decay becomes the dominating opacity source for low-energyνe. Accurate three-flavor Boltzmann neutrino transport enables us to relate the magnitude of neutrino fluxes and spectra to details of the treatment of weak processes. This allows us to quantify the corresponding impact on the conditions relevant for the nucleosynthesis in the neutrino-driven wind, which is ejected from the proto-neutron star surface during the deleptonization phase.

Improved neutrino-nucleon interactions in dense and hot matter for numerical simulations

“…From this change in (anti-)neutrino distribution function we can deduce the (anti-)neutrino emissivity j and the inverse mean free path 1/λ which are related to the creation and absorption rates via (13) for neutrinos and (14) for anti-neutrinos. The above expressions only explicitly contain the contribution of electronic processes and positronic ones have to be added in order to obtain the complete emissivity and mean free path.…”

“…The heating by neutrinos of the stalled shock wave represents a crucial element for the dynamics of core-collapse supernovae (CCSN), contributing to the explosion mechanism Simulations of these processes are very expensive, so that currently mostly analytic expressions for the relevant reaction rates [2][3][4][5] are applied, which are, however, often based on very crude approximations. Several corrections have been added to the original expressions [2], such as weak magnetism and recoil [6], nuclear structure corrections [7,8], effective masses and chemical potentials for nucleons in dense matter [9][10][11], additional reactions [12,13] and superfluidity in cooling neutron stars older than several minutes [14]. Several authors have, however, pointed out since decades that in dense matter different effects can additionally modify the neutrino matter interaction rates and neutrino emissivities by orders of magnitude, in particular nuclear correlations [15][16][17][18][19][20][21].…”

“…In view of the computational effort, only few simulations go indeed beyond the analytical expressions. In particular, the full phase space has been considered in several PNS cooling simulations [10,26] as well as for charged-current opacities in the spherically symmetric CCSN simulations of Fischer et al [13] and the Garching group has implemented additionally nuclear correlations following the simplified formalism of Burrows and Sawyer [15,16], see Buras et al [27] and Hüdepohl et al [28]. However, as for neutrino-nucleus reactions, where already for a long time tabulated and accurate data on selected nuclei from microscopic calculations accounting for nuclear correlations and thermal effects exist [29][30][31][32][33][34], it is desirable that im-proved rates for neutrino-nucleon reactions become more generally available.…”

“…neutrino absorption and creation. We will stick to non-relativistic kinematics, but in addition to the full phase space, which is important at high densities [13,24], we will include nuclear correlations via the so-called "Random Phase Approximation"(RPA). The impact of RPA correlations on neutrino opacities has been studied in several works, see e.g.…”

“…[17]. In contrast to Roberts and Reddy [24] who provide routines and Fischer et al 1 https://compose.obspm.fr [13] who use a phase space integration "on the fly" during spherically symmetric simulations, we have chosen to directly provide opacity tables since the numerical calculations to obtain the rates in RPA (and probably any other scheme taking into account nuclear correlations) are much more time consuming than the simpler phase space integrations due to the existence of collective excitations in the nuclear response, see e.g. [36].…”