Constraining black holes with light boson hair and boson stars using epicyclic frequencies and quasiperiodic oscillations

Franchini, Nicola; Pani, Paolo; Maselli, Andrea; Gualtieri, Leonardo; Herdeiro, Carlos A.R.; Radu, Eugen; Ferrari, Valeria

Abstract

Light bosonic fields are ubiquitous in extensions of the Standard Model. Even when minimally coupled to gravity, these fields might evade the assumptions of the black-hole no-hair theorems and give rise to spinning black holes which can be drastically different from the Kerr metric. Furthermore, they allow for self-gravitating compact solitons, known as (scalar or Proca) boson stars. The quasiperiodic oscillations (QPOs) observed in the x-ray flux emitted by accreting compact objects carry information about the strong-field region, thus providing a powerful tool to constrain deviations from Kerr’s geometry and to search for exotic compact objects. By using the relativistic precession model as a proxy to interpret the QPOs in terms of geodesic frequencies, we investigate how the QPO frequencies could be used to test the no-hair theorem and the existence of light bosonic fields near accreting compact objects. We show that a detection of two QPO triplets with current sensitivity can already constrain these models and that the future eXTP mission or a LOFT-like mission can set very stringent constraints on black holes with bosonic hair and on (scalar or Proca) boson stars. The peculiar geodesic structure of compact scalar/Proca boson stars implies that these objects can easily be ruled out as alternative models for x-ray source GRO J1655-40.

Citation

Franchini, N., Pani, P., Maselli, A., Gualtieri, L., Herdeiro, C. A., Radu, E., & Ferrari, V. (2017). Constraining black holes with light boson hair and boson stars using epicyclic frequencies and quasiperiodic oscillations. Physical Review D, 95(12), Article 124025. https://doi.org/10.1103/PhysRevD.95.124025

• Journal Article Type: Article
• Acceptance Date: Jun 1, 2017
• Publication Date: Jun 14, 2017
• Deposit Date: Sep 8, 2017
• Publicly Available Date: Sep 8, 2017
• Journal: Physical Review D
• Print ISSN: 2470-0010
• Electronic ISSN: 2470-0029
• Publisher: American Physical Society
• Peer Reviewed: Peer Reviewed
• Volume: 95
• Issue: 12
• Article Number: 124025
• DOI: https://doi.org/10.1103/PhysRevD.95.124025
• Public URL: https://nottingham-repository.worktribe.com/output/866313
• Publisher URL: https://journals.aps.org/prd/abstract/10.1103/PhysRevD.95.124025
• Additional Information: © 2017 American Physical Society