Constraining the Spin-Orbit Orientation of X-ray Pulsars through Phase-Resolved Spectroscopy

Project Description

In binary systems, the rotational and orbital angular momentum vectors are typically assumed to be co-aligned. However, this is not always the case. For example, Venus exhibits retrograde rotation relative to its orbital plane, and similar misalignments have been discovered in various exoplanetary systems. These examples indicate that spin-orbit alignment can be disrupted during the formation or early evolution of stellar and planetary systems. In X-ray binaries, such misalignments may be even more significant due to the asymmetric kicks of supernova explosions. Using X-ray spectroscopy, it is possible to probe the spin-orbit geometry by measuring the time delay between the pulsar beam and the irradiated fluorescent spectral lines from the companion. This project will perform timing-spectroscopic analysis using Chandra, XMM-Newton, or XRISM to determine the spatial orientation between the neutron star and its companion in high-mass X-ray binary systems.