Description du projet
Une étude pourrait permettre de mieux comprendre la matière ultradense des étoiles à neutrons
Les étoiles à neutrons sont constituées de matière nucléaire soumise à des conditions de densité extrêmement élevée et offrent la possibilité de trouver des états stables de matière à quarks étranges. Notre incertitude relative à la nature de la matière froide ultradense est encodée dans l’équation d’état, qui peut être mise en correspondance avec des quantités telles que la masse et le rayon, via les équations de la structure stellaire. Le projet AEONS, financé par l’UE, affine une nouvelle technique de mesure de la masse et du rayon qui exploite les effets relativistes sur les rayons X émis par les points chauds à la surface de l’étoile à neutrons: la modélisation du profil de pulsation. À l’aide des données fournies par le Neutron Star Interior Composition Explorer de la NASA et dans la perspective de la prochaine génération de télescopes spatiaux à rayons X, AEONS cherche à établir des contraintes strictes applicables aux modèles de matière dense.
Objectif
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.
Champ scientifique
- natural sciencesphysical sciencesastronomyobservational astronomygravitational waves
- natural sciencesphysical sciencesastronomystellar astronomyneutron stars
- natural sciencesmathematicsapplied mathematicsstatistics and probabilitybayesian statistics
- natural sciencesphysical sciencestheoretical physicsparticle physicsquarks
Programme(s)
Régime de financement
ERC-COG - Consolidator GrantInstitution d’accueil
1012WX Amsterdam
Pays-Bas