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

Kavli Affiliate: Lijing Shao

| First 5 Authors: Zexin Hu, Yong Gao, Rui Xu, Lijing Shao,

| Summary:

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{`e}se theory, the
Mendes-Ortiz theory, and the $xi$-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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