Orbital-period Changes of Low-mass X-ray Binaries Driven by Magnetic Braking

TL;DR

This study uses the CARB magnetic braking model within binary evolution simulations to successfully explain the observed orbital period changes and other properties of several low-mass X-ray binaries, including neutron star and black hole systems.

Contribution

It demonstrates that the CARB magnetic braking prescription can accurately reproduce observed properties of certain LMXBs, improving understanding of their evolution.

Findings

Successfully reproduces observed donor masses and period derivatives for multiple LMXBs.

Aligns effective temperatures with observed spectral types.

Standard magnetic braking models struggle to match rapid orbital changes.

Abstract

The magnetic braking (MB) plays an important role in driving the evolution of low-mass X-ray binaries (LMXBs). The modified MB prescription, convection and rotation boosted (CARB) model, is very successful in reproducing the detected mass-transfer rates of persistent neutron star (NS) LMXBs. In this work, we investigate whether the CARB MB prescription could account for the formation and evolution of some NS and black hole (BH) LMXBs with an observed orbital period derivative. Using the MESA code, we perform a detailed binary evolution model for six NS and three BH LMXBs. Our simulations find that the CARB MB prescription can successfully reproduce the observed donor-star masses, orbital periods, and period derivatives of four NS LMXBs and one BH LMXB. Our calculated effective temperatures are in good agreement with the detected spectral types of two NS LMXBs and one BH LMXB. However, the standard MB model is difficult to produce the observed period derivatives of those LMXBs experiencing a rapid orbital shrinkage or expansion.