Work

Massive scalar fields in eccentric regime: Detectability and constraints from LISA observations of extreme mass-ratio inspirals

Year: 2026

Type: article

Abstract: Extreme mass-ratio inspirals (EMRIs) are among the most promising sources for future space-based gravitational wave (GW) observatories and provide sensitive probes of additional fundamental fields in the strong-gravity regime. In the present work, we investigate eccentric equatorial EMRIs around Kerr black holes in the presence of a massive scalar field. We assume that the inspiralling object carries a scalar charge, therefore, emits scalar radiation in addition to GWs. By solving the massive scalar perturbation equation in the frequency domain, we compute the relativistic scalar energy fluxes at the event horizon and at infinity and incorporate them into an adiabatic inspiral model. We investigate the impact of the scalar charge and scalar field mass on the orbital evolution and gravitational waveforms by analysing the accumulated phase differences and waveform mismatches relative to both general relativity (GR) and the massless scalar limit. Our results show that the massive scalar radiation can produce significant GW dephasing, with the effect becoming increasingly pronounced for more eccentric orbits. In addition, the scalar flux is suppressed for larger scalar field masses as fewer scalar harmonics satisfy the propagation condition at infinity. Finally, using both Fisher-information-matrix forecasts and Bayesian parameter estimation, we assess the capability of the Laser Interferometer Space Antenna to constrain the scalar charge and scalar field mass. The two inference approaches gives consistent constraints, demonstrating that eccentric EMRIs provide a promising avenue for probing massive scalar fields and scalar-tensor extensions of gravity in the strong-field regime.

Source: Physical review. D/Physical review. D.

DOI: 10.1103/419g-dkvb

Authors: Tieguang Zi, Shailesh Kumar, Genliang Li, Jun-Kun Zhao, Bao-Min Gu, Fu-Wen Shu

Institutions: Nanchang University, Putian University

Language: English

Topic: Pulsars and Gravitational Waves Research

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: green

Funders: National Natural Science Foundation of China, Natural Science Foundation of Jiangxi Province, Nanchang University, Indian Institute of Technology Kharagpur

Awards: G2892431678, G3582149519, G4666040506, G8967364994, G945036164