Speaker
Description
Neutron stars (NSs) in quiescent low-mass X-ray binaries (qLMXBs) have been used in the past two decades for mass and radius measurements to better constrain the equation-of-state of dense matter. However, various sources of systematic uncertainties were put forward, possibly biasing the radius values by as much as 50%. They include the unknown NS spin and atmospheric composition, as well as possible surface anisotropies.
A new method, inspired from pulse-profile modeling (PPM) of millisecond pulsars (MSPs), has recently been developed to constrain masses and radii of qLMXBs by including rotation and hot spots in the spectral modeling.
We will show that NewAthena will significantly improve these measurements thanks to its effective area, yielding an excellent signal-to-noise ratio (SNR). This will put more stringent constraints on the possibility of hot spots or on the spectral broadening due to the NS rotation. NewAthena’s time resolution will also allow to search for pulsations from these systems. Finally, the atmosphere composition can be determined thanks to observations of the NS binary companion with JWST, or with the ELT in the near-future.
All in all, this new method free of systematic biases combined to NewAthena’s excellent SNR will provide EOS constraints from qLMXBs on a par with PPM of MSPs.
