Pulse profile modeling of thermonuclear burst oscillations*

Pulse profile modeling (PPM) is a sophisticated relativistic ray-tracing technique used to deduce key parameters such as the mass, radius, and surface characteristics of neutron stars. It is the technique being used by the Neutron Star Interior Composition Explorer (NICER) collaboration to constrain the properties of rotation-powered millisecond pulsars (RMPs).PPM can also be applied to thermonuclear burst oscillation (TBO) sources, accreting neutron stars that develop surface hotspots during thermonuclear explosions (Type I X-ray bursts), and this is a major science goal for future large-area X-ray spectral-timing telescopes. TBO sources have higher spin rates than most RMPs, promising more precise constraints on the mass and radius. The abundance of sources enhances the prospects of sampling a wider spectrum of masses and radii, thereby reducing statistical uncertainties. And multiple opportunities exist for independent cross-verification through complementary constraints, mitigating potential systematic errors. However, TBO sources also present a significant challenge due to their inherent and dramatic short-time-scale variability. I will outline analysis methods that we have developed to accurately determine the properties of TBO sources using PPM and present results for the TBO source XTE J1814−338.