Probing dark matter with neutron stars and their mergers

by Dr Violetta Sagun (University of Southampton)

Wednesday 28 Oct 2026, 11:30 → 12:30 Europe/London

R61 CR03 (RAL)

Abstract: 

Compact stars due to their enormous gravitational field can accumulate a significant amount of dark matter in their interior. Depending on its nature, accumulated dark matter may affect the properties of neutron stars in quite different ways. I will give an overview of the impact of dark matter on various observable properties of neutron stars, i.e. gravitational mass, radius, moment of inertia, matter distribution, thermal evolution, etc. For two scenarios, asymmetric fermionic and bosonic dark matter, the conditions at which dark matter particles tend to condense in the core of the star or create an extended halo will be presented. I will show how dark matter condensed in a core tends to decrease the total gravitational mass and tidal deformability compared to a pure baryonic star, which appears as an effective softening of the equation of state. On the other hand, the presence of a dark matter halo has the opposite effect, causing an increase in those observable quantities. Thus, observational data on compact stars could be affected by accumulated dark matter and, consequently, constraints we put on the strongly interacting matter at high densities.

 

While neutron stars provide a compelling testing ground for gravity, nuclear physics, and physics Beyond the Standard Model, the possible degeneracy between the effect of dark matter or gravity beyond GR and dense matter properties could lead to misleading conclusions while analysing the observational data. I will discuss how the joint efforts of multi-messenger observations of neutron stars along with the experimental and theoretical subatomic physics are pivotal for breaking a possible degeneracy and shedding light on the neutron star internal composition.

 

About Speaker:

 

Dr. Violetta Sagun is a Senior Researcher at the Southampton Theory, Astrophysics and Gravity (STAG) Research Centre, University of Southampton, working at the intersection of nuclear physics, compact stars, dark matter, and gravitational-wave astronomy. Her research focuses on multi-messenger probes of fundamental physics, with particular emphasis on the impact of dark matter on neutron stars and their mergers, the equation of state of strongly interacting matter, and the search for deconfined quark matter in neutron-star interiors. Her research explores how fundamental physics can be probed through neutron stars, their mergers, and multi-messenger observations.

 

Dr. Sagun is Chair of the Cosmic Explorer Dark Matter Group, where she coordinates the group’s activities and leads the development of its Science Traceability Matrix. She is also an active member of the Einstein Telescope, SKA, and NewAthena collaborations, working on the use of next-generation gravitational-wave, radio, and X-ray observatories to probe dense matter and dark matter.

 

Another direction of her research focuses on strongly interacting matter across a wide range of temperatures and densities, connecting the physics of heavy-ion collisions with that of neutron stars and using multi-messenger observations to probe the QCD phase diagram and the properties of dense matter.

 

 

Zoom room