Quasi-universal relations for the masses and radii of rotating neutron stars

Over the next few years, it is expected that present (eg NICER, LIGO, CHANDRA, XMM) and planned (eg ATHENA, STROBE-X, eXTP) telescopes will be providing precise measurements of the masses and radii of many neutron stars, allowing for a determination of the equation of state of cold supranuclear density matter. The neutron stars' properties will be determined using a variety of methods, all with systematic errors. The different methods and telescopes target neutron stars with different spin rates which introduces another complication, since the rotation of a star increases its mass and radius. Many properties of rotating neutron stars have been shown to obey universal relationships. In this work we explore the extent to which the increase and mass and radius due to rotation follows a universal type of relation and how this can be used to compare equation of state constraints resulting from different methodologies.