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arXiv · 2509.07767

Illuminating dark matter admixed in neutron stars with simultaneous mass-radius constraints

Nai-Bo Zhang·Bao-An Li·Jia-Yu Zhang·Wei-Na Shen·Hui Zhang
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Abstract

We investigate how simultaneous mass and radius measurements of massive neutron stars (NSs) can help constrain properties of dark matter (DM) possibly admixed in them. Within a fermionic DM model that interacts only through gravitation, along with a well-constrained nuclear matter equation of state, we show that the simultaneous mass and radius measurement of PSRJ0740+6620 reduces the uncertainty of DM central energy density by more than 50\% compared to the results obtained from using the two observables independently, while other DM parameters remain unconstrained. Additionally, we find that the DM fraction $f_D$ should be smaller than 2\% when constrained by the observed NS maximum mass alone, and it could be even smaller than 0.3\% with the simultaneous measurement of mass and radius, supporting the conclusion that only a small amount of DM exists in DM admixed neutron stars (DANS).

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Nai-Bo Zhang, Bao-An Li, Jia-Yu Zhang, Wei-Na Shen, Hui Zhang. 2025-09-09. Illuminating dark matter admixed in neutron stars with simultaneous mass-radius constraints. https://doi.org/10.3390/sym17101669

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