Neutron Stars in X-ray Binaries and their Environments

TL;DR

This paper reviews the complex interactions and recent developments in understanding neutron stars within X-ray binaries, focusing on accretion processes, environmental effects, and orbital evolution insights from X-ray observations.

Contribution

It provides a comprehensive overview of recent advances in understanding neutron star interactions, accretion dynamics, and orbital evolution in X-ray binary systems.

Findings

Detailed models of accretion stream structure and pulse profile changes.

Observations of orbital period glitches and potential circum-binary planets.

Insights into the vertical structure of accretion disks and wind interactions.

Abstract

Neutron stars in X-ray binary systems are fascinating objects that display a wide range of timing and spectral phenomena in the X-rays. Not only parameters of the neutron stars, like magnetic field strength and spin period evolve in their active binary phase, the neutron stars also affect the binary systems and their immediate surroundings in many ways. Here we discuss some aspects of the interactions of the neutron stars with their environments that are revelaed from their X-ray emission. We discuss some recent developments involving the process of accretion onto high magnetic field neutron stars: accretion stream structure and formation, shape of pulse profile and its changes with accretion torque. Various recent studies of reprocessing of X-rays in the accretion disk surface, vertical structures of the accretion disk and wind of companion star are also discussed here. The X-ray pulsars among the binary neutron stars provide excellent handle to make accurate measurement of the orbital parameters and thus also evolution of the binray orbits that take place over time scale of a fraction of a million years to tens of millions of years. The orbital period evolution of X-ray binaries have shown them to be rather complex systems. Orbital evolution of X-ray binaries can also be carried out from timing of the X-ray eclipses and there have been some surprising results in that direction, including orbital period glitches in two X-ray binaries and possible detection of the most massive circum-binary planet around a Low Mass X-ray Binary.