NICER and the properties of dense matter in neutron stars

Precise and reliable measurements of neutron star radii and other properties are essential to our understanding of cold, catalyzed matter beyond nuclear saturation density. Over the last fifteen years, measurements of high-mass neutron stars, gravitational waves from the double neutron star merger GW170817, and X-ray observations have dramatically improved our understanding of neutron star structure. In particular, NASA’s Neutron star Interior Composition Explorer (NICER) satellite has provided high-quality data sets that have yielded published measurements of the mass and radius of several neutron stars. I will discuss our group’s analyses of these pulsars and will in particular discuss our assumptions and potential systematic errors, to help in the assessment of our work. I will also discuss the implications of our results, combined with other observations, for the properties of the dense matter in the cores of neutron stars.