The Radius of the High Mass Pulsar PSR J0740+6620 With 3.6 Years of NICER Data

Determination of the masses and radii of a set of neutron stars (NSs) can be used to infer properties of the high-density matter in their cores. This is possible due to the one-to-one mapping between the dense matter equation of state (EoS) and the mass–radius dependence of the NS. One way to measure the masses and radii of NSs is to model their X-ray pulses which depend on the general and special relativistic effects when photons are transported from hot regions at the stellar surface to the observer. During the last few years, NICER telescope has applied this technique to two millisecond pulsars; PSR J0030+0451 and the heavy pulsar PSR J0740+6620. In this talk, I will present the updated results for the latter, using the X-PSI code, with a new NICER data set with more than 0.5 million additional observed photons, a substantial increase in data set size compared to previous analyses. The results continue to disfavor the softest EoSs and provide tighter constraints to the heated surface regions of the NS.