https://doi.org/10.1140/epjc/s10052-025-14990-5
Regular Article - Theoretical Physics
Eccentric extreme-mass-ratio inspirals: a new window into ultra-light vector fields
1
Department of Physics, Nanchang University, 330031, Nanchang, China
2
Center for Relativistic Astrophysics and High Energy Physics, Nanchang University, 330031, Nanchang, China
3
School of Physics and Optoelectronics, South China University of Technology, 510641, Guangzhou, People’s Republic of China
a
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Received:
21
September
2025
Accepted:
24
October
2025
Published online:
5
November
2025
Abstract
Space-based gravitational-wave detectors, such as the Laser Interferometer Space Antenna (LISA), provide a platform to probe new fundamental fields through extreme-mass-ratio inspirals (EMRIs), where a compact secondary object carrying scalar or vector charges inspirals into a massive primary. In a theory-agnostic framework, we compute the ultra-light vector and gravitational radiation emitted by eccentric EMRIs and determine the corresponding inspiral trajectories. We evaluate the impact of a massive vector (Proca) field on EMRIs waveform through dephasing and mismatches with predictions by general relativity. Using a Fisher information matrix analysis, we further assess LISA’s capability to constrain the Proca mass from future EMRIs observations. We find that orbital eccentricity can improve estimation accuracy of parameters, making the vector mass 
become detectable for the case of 
. Correlation analysis further reveals strong positive dependencies between the Proca mass and intrinsic source parameters, indicating that improved measurement of these parameters directly tightens constraints on vector mass. These results demonstrate that high-eccentricity EMRIs observed by LISA offer a powerful channel to detect or constrain massive vector-field extensions of GR in the strong-field regime.
© The Author(s) 2025
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Funded by SCOAP3.
