2010/08/30 by Liu Men-Quan, Men-Quan Liu
Physics and Astronomy · #Cosmology and Gravitation Theories #Gamma-ray bursts and supernovae #High-Energy Particle Collisions Research #Nuclear astrophysics #Nuclear physics #Physics #Thermodynamics #astro-ph.HE
paper · pdf · doi:10.1088/1674-4527/11/1/005
11 pages, 4 figures, accepted for publication in Research in Astronomy and Astrophysics
arxiv created 2010/08/30 · openalex publication_date 2010/12/22 · arxiv updated 2015/05/19 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
The steady equilibrium conditions for a mixed gas of neutrons, protons, electrons, positrons and radiation fields (abbreviated as npe ± gas) with or without external neutrino flux are investigated, and a general chemical potential equilibrium equation μ n = μ p + C μ e is obtained to describe the steady equilibrium at high temperatures ( T > 10 9 K). An analytic fitting formula of coefficient C is presented for the sake of simplicity, when neutrinos and antineutrinos are transparent. It is a simple method to estimate the electron fraction for the steady equilibrium npe ± gas that adopts the corresponding equilibrium condition. As an example, we apply this method to the GRB accretion disk and confirm that the composition in the inner region is approximately in equilibrium when the accretion rate is low. For the case with external neutrino flux, we calculate the initial electron fraction of neutrino-driven wind from the proto-neutron star model M15-l1-r1. The results show that the improved equilibrium condition makes the electron fraction decrease significantly more than the case μ n = μ p + μ e when the time is less than 5 s post bounce, which may be useful for r-process nucleosynthesis models.