The r-Java 2.0 code: nuclear physics

Abstract

Aims. We present r-Java 2.0, a nucleosynthesis code for open use that performs r-process calculations, along with a suite of other analysis tools. Methods. Equipped with a straightforward graphical user interface, r-Java 2.0 is capable of simulating nuclear statistical equilibrium (NSE), calculating r-process abundances for a wide range of input parameters and astrophysical environments, computing the mass fragmentation from neutron-induced fission and studying individual nucleosynthesis processes. Results. In this paper we discuss enhancements to this version of r-Java, especially the ability to solve the full reaction network. The sophisticated fission methodology incorporated in r-Java 2.0 that includes three fission channels (beta-delayed, neutron-induced, and spontaneous fission), along with computation of the mass fragmentation, is compared to the upper limit on mass fission approximation. The effects of including beta-delayed neutron emission on r-process yield is studied. The role of Coulomb interactions in NSE abundances is shown to be significant, supporting previous findings. A comparative analysis was undertaken during the development of r-Java 2.0 whereby we reproduced the results found in the literature from three other r-process codes. This code is capable of simulating the physical environment of the high-entropy wind around a proto-neutron star, the ejecta from a neutron star merger, or the relativistic ejecta from a quark nova. Likewise the users of r-Java 2.0 are given the freedom to define a custom environment. This software provides a platform for comparing proposed r-process sites.

Limits on active-sterile neutrino mixing parameters using heavy nuclei abundances

“…If tsta relaxes to a value of the order of the age of the Universe, the heaviest nuclei (masses (A > 200)), decay to 232 Th, 235 U and 238 U. We have adopted, for the stability time, the value tsta = 4.354×10 17 s. 43,44,51 Since in the calculations only the production of nuclei through the r-process is considered, we have restricted the observational data 53 to the abundances produced primarily through it. [54][55][56][57] The observational data are shown in Table 1.…”

“…To perform the calculations we have chosen the r-java2.0 code, developed by the Calgary University group. [43][44][45] This code solves the nuclear r-process network coupled to an astrophysical scenario. We have modified the inputs of the code to include the βdecay rates of Eq.…”

“…To characterize the neutrino wind, we have chosen the initial temperature as T 0 = 3 × 10 9 K, the density profile ρ = ρ 0 (1+t/(2τ )) 2 where the initial density is ρ 0 = 10 11 g/cm 3 and the expansion time-scale is τ = 0.1 s. The wind speed of expansion was set to Vexp = 7500 km/s and the initial wind radius fixed at R 0 = 390 km. 41,43,44,[46][47][48] b) a neutron-star merger (NSm);…”

“…This environment was characterized by an initial temperature T 0 = 3 × 10 9 K and the polytropic profile P = Kρ (n+1)/n where the polytropic index is fixed at n = 1.5 and K is constant. 44 The initial density and the internal pressure were set to ρ 0 = 10 11 g/cm 3 and P 0 = 0.005 MeV/fm 3 respectively. Finally, the expansion velocity was fixed at Vexp = 1.9×10 5 km/s and the initial radius of the ejecta at R 0 = 2 km.…”

“…For the neutron-star mergers we have considered two values for Ye, namely 0.1 and 0.3, and performed a combination of both computed abundances to obtain their final values, as done in. 44,51,52…”