Project description
Research could shed more light on ultradense neutron star matter
Neutron stars are made of nuclear matter under extremely high-density conditions and offer the possibility of finding stable states of strange quark matter. Our uncertainty about the nature of cold ultradense matter is encoded in the equation of state, which can be mapped via the stellar structure equations to quantities like mass and radius. The EU-funded AEONS project is refining a newly developed technique for measuring mass and radius that exploits relativistic effects on X-rays emitted from hotspots on the neutron star’s surface: pulse profile modelling. Using data from NASA's Neutron Star Interior Composition Explorer and looking ahead to the next generation of X-ray space telescopes, AEONS seeks to place tight constraints on dense matter models.
Objective
Densities in neutron star (NS) cores can reach up to ten times the density of a normal atomic nucleus, and the stabilising effect of gravitational confinement permits long-timescale weak interactions. This generates nucleonic matter that is extremely neutron-rich, and the exciting possibility of stable states of strange matter (hyperons or deconfined quarks). Our uncertainty about the nature of cold ultradense matter is encoded in the Equation of State (EOS), which can be mapped via the stellar structure equations to quantities like mass M and radius R that determine the exterior space-time.
One very promising technique for measuring the EOS exploits hotspots that form on the NS surface due to the pulsar mechanism, accretion streams, or during thermonuclear explosions in the stellar ocean. As the NS rotates, the hotspot gives rise to a pulsation and relativistic effects encode information about the EOS into the pulse profile. Pulse Profile Modelling (PPM), which employs relativistic ray-tracing and Bayesian inference codes to measure M-R and the EOS, is being pioneered by NASA’s NICER telescope, which is poised to deliver its first results in 2019.
Complexities, that have only become apparent with exposure to real data, mean that there is work to be done if we are to have confidence in the nominal 5-10% accuracy of NICER’s M-R results. AEONS will deliver this. The project will also look ahead to the next generation of large-area X-ray timing telescopes, since it is only then that PPM will place tight constraints on dense matter models. The sources these missions target, accreting neutron stars, pose challenges for PPM such as variability, surface pattern uncertainty, and polarimetric signatures. AEONS will develop a robust pipeline for accreting NS PPM and embed it in a multi-messenger EOS inference framework with radio and gravitational wave constraints. This will ensure that PPM delivers major advances in our understanding of the nature of matter.
Fields of science
- natural sciencesphysical sciencesastronomyobservational astronomygravitational waves
- natural sciencesphysical sciencesastronomystellar astronomyneutron stars
- natural sciencesmathematicsapplied mathematicsstatistics and probabilitybayesian statistics
- natural sciencesphysical sciencestheoretical physicsparticle physicsquarks
Programme(s)
Funding Scheme
ERC-COG - Consolidator GrantHost institution
1012WX Amsterdam
Netherlands