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arXiv · 2109.13453

Scalarized neutron stars in massive scalar-tensor gravity: X-ray pulsars and tidal deformability

Zexin Hu·Yong Gao·Rui Xu·Lijing Shao
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Abstract

Neutron stars (NSs) in scalar-tensor theories of gravitation with the phenomenon of spontaneous scalarization can develop significant deviations from general relativity. Cases with a massless scalar were studied widely. Here we compare the NS scalarizations in the Damour--Esposito-Far{è}se theory, the Mendes-Ortiz theory, and the $ξ$-theory with a massive scalar field. Numerical solutions for slowly rotating NSs are obtained. They are used to construct the X-ray pulse profiles of a pair of extended hot spots on the surface of NSs. We also calculate the tidal deformability for NSs with spontaneous scalarization which is done for the first time with a massive scalar field. We show the universal relation between the moment of inertia and the tidal deformability. The X-ray pulse profiles, the tidal deformability, and the universal relation may help to constrain the massive scalar-tensor theories in X-ray and gravitational-wave observations of NSs, including the Neutron star Interior Composition Explorer (NICER) satellite, Square Kilometre Array (SKA) telescope, and LIGO/Virgo/KAGRA laser interferometers.

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Zexin Hu, Yong Gao, Rui Xu, Lijing Shao. 2025-03-31. Scalarized neutron stars in massive scalar-tensor gravity: X-ray pulsars and tidal deformability. https://doi.org/10.1103/physrevd.104.104014

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