arXiv subjects

Seppe J. Staelens

Publications and source records attributed to Seppe J. Staelens.

5 recordsLinked to original sources

arXiv2026

Black Hole-Boson Star Binaries: Gravitational Wave Signals and Tidal Disruption

We present a detailed, fully nonlinear study of binary systems involving one black hole and one boson star, considering the effects of both a quartic self-interaction and a solitonic potential for the scalar field. First, we show the importance of using initial data for which the boson star is in an equilibrated configuration to obtain accurate gravitational waveforms, and discuss methods to further improve constraint violations in the initial data. We then present a series of head-on collisions, showing that even in this simplified scenario the radiative efficiency varies significantly with the scalar potential chosen. In addition to this, we present a preliminary study of inspiral configurations, showing that an appropriate scalar self-interaction can suppress tidal disruption. We comment throughout on implications for attempts to build model-agnostic waveform template banks for exotic compact objects.

gr-qc↗

arXiv2026

The Shape of Eccentricity: Rapid Classification of Eccentric Binaries with the Wavelet Scattering Transform

The gravitational-wave (GW) detections reported by the LIGO-Virgo-KAGRA (LVK) collaboration have so far been consistent with quasi-circular compact binary coalescences (CBCs). Nevertheless, a small fraction of binaries driven to merge through dynamical interactions in dense stellar environments or in field triples may retain measurable orbital eccentricity when entering the sensitive frequency band of LVK detectors. Confident measurement of eccentricity in the LVK band would provide strong evidence for such dynamically driven mergers; however, eccentric gravitational-waveform models are computationally expensive, and performing production-level inference on all detected signals is not an efficient use of resources when eccentric signals are expected to be rare. An intermediate step between detection and analysis, in which the signal is assessed for the potential presence of eccentricity, could provide quick recommendations for which signals should undergo full eccentric inference. We apply the wavelet scattering transform (WST) to a large set of synthetic waveforms in realistic noise and assess its discriminatory power using simple linear and shallow neural-network classifiers. We find that the WST representation enables effective discrimination between eccentric and quasi-circular binaries and provides a compact multi-scale representation of GW signals. Our approach achieves ~64% percent detection accuracy at a false alarm rate of 10%, with an AUC of 0.844 and an average precision of 0.876. We also examine the ability of our classifiers to distinguish eccentricity from spin-induced precession and find robust performance across a range of spin-precession magnitudes.

gr-qc↗

arXiv2026

Long-term stable nonlinear evolutions of ultracompact black-hole mimickers

We study the stability of ultracompact boson stars admitting light rings combining a perturbative analysis with 3+1 numerical-relativity simulations with and without symmetry assumptions. We observe excellent agreement between all perturbative and numerical results which uniformly support the hypothesis that this family of black-hole mimickers is separated into stable and unstable branches by extremal-mass configurations. This separation includes, in particular, thin-shell boson stars with light rings located on the stable branch which we conclude to represent long-term stable black-hole mimickers.

gr-qc↗

arXiv2026

Ray tracing ultracompact boson stars: visibility modulations and incomplete photon rings

Modified black holes and black hole mimickers can give rise to additional photon rings in ray-traced images. With the photon ring structure of Kerr well understood, the question arises how well future versions of the Event Horizon Telescope images would be able to constrain the presence of non-Kerr photon rings. In this work, we investigate how likely additional photon rings are to present themselves through low-frequency modulations of the visibility amplitude, i.e. in Fourier space where the data live. To this end, we generate ray-traced images of stable and unstable ultracompact, solitonic boson stars, both in spherical symmetry and with rotation. We find that clear modulations in the associated visibility amplitude are only present in spherical symmetry, for a restricted range of observer inclinations, hence suggesting that these modulations can not be a generic expectation of ultracompact black-hole mimickers. Additionally, we discuss how the photon rings are incomplete for the rotating boson stars considered, and how an unstable prograde light ring may be needed to remedy this.

gr-qc↗

arXiv2026

Search for growing angular modes in ultracompact boson star evolutions

Recent fully non-linear simulations of ultracompact spherically symmetric boson stars have presented evidence for their long-term stability. All observed dynamics could be mainly attributed to the fundamental radial mode. In this work, we additionally decompose some of the data in spherical harmonics, providing a first step towards the characterization of non-spherical modes present.

gr-qc↗