Monte Carlo population synthesis of post-common-envelope white dwarf binaries and type Ia supernova rate

TL;DR

This study uses Monte Carlo binary population synthesis to explore the evolution of white dwarf binaries and estimate the type Ia supernova rate, considering various physical assumptions and initial conditions.

Contribution

It introduces a comprehensive Monte Carlo BPS simulation framework with multiple assumptions on physical processes, providing new insights into WD binary populations and supernova progenitors.

Findings

Larger post-CE WD/MS binaries form with lambda_e energy parameter.

Orbital period and mass distributions are affected by input parameters.

The merger rate of double WDs is compared to the SNe Ia rate.

Abstract

Binary population synthesis (BPS) study provides a comprehensive way to understand evolutions of binaries and their end products. Close white dwarf (WD) binaries have crucial characteristics in examining in uence of yetunresolved physical parameters on the binary evolution. In this paper, we perform Monte Carlo BPS simulations, investigating the population of WD/main sequence (WD/MS) binaries and double WD binaries, with a publicly available binary star evolution code under 37 different assumptions on key physical processes and binary initial conditions. We considered different combinations of the binding energy parameter (lambda_g:considering gravitational energy only, lambda_b: considering both gravitational energy and internal energy, and lambda_e:considering gravitational energy, internal energy, and entropy of the envelope, the values of them derived with the MESA code), CE effciency, critical mass ratio, initial primary mass function and metallicity. We find that a larger number of post-CE WD/MS binaries in tight orbits are formed when the binding energy parameters is set by lambda_e than the cases adopting the other prescriptions. We also find effects of the other input parameters on orbital period and mass distributions of post-CE WD/MS binaries as well. Containing at least one CO WD, the double WD system evolved from WD/MS binaries may explode as type Ia supernovae (SNe Ia) by merging. In this work, we also investigate a frequency of two WD mergers and compare it to the SNe Ia rate.