Speaker
Description
The Equation of State (EoS) of ultra-dense matter inside Neutron Stars (NS) is one of the long-standing questions of modern astrophysics and a key science goal of NewAthena. To constrain the composition of this dense matter, we measure the macroscopic observables of NSs, such as their masses and radii. The most precise method to measure the radius of NSs is Pulse Profile Modeling (PPM), where we model the X-ray surface emission of millisecond pulsars (MSPs). These models are fitted to phase-resolved X-ray observations of MSPs, which allows us to constrain their radius.
As MSPs are faint sources, this method requires a low background and a large collecting area, along with timing capabilities. To achieve this, we currently exploit megasecond long phase-resolved Neutron Star Interior Composition ExploreR (NICER) spectra associated with phase-averaged XMM-Newton spectra. This results in four exploitable radius measurements with $\pm 1\,$km (~10%) uncertainties.
In this talk, I will present the future performances of NewAthena to constrain the EoS of dense matter with PPM. NewAthena meets all of the requirements to perform PPM without the need for NICER or XMM-Newton data. We expect the individual radius measurement uncertainties to decrease down to $\pm 300\,$m, with an exposure of ~200 ks per source, which will put tight constraints on the EoS. I will also present the capabilities of NewAthena to differentiate between NS surface emission models, such as the atmosphere composition, or between different geometric configurations of the emission regions.
