The gravitational afterglow of boson stars

Croft, Robin; Helfer, Thomas; Ge, Bo-Xuan; Radia, Miren; Evstafyeva, T.; Lim, Eugene A.; Sperhake, Ulrich; Clough, Katy

doi:10.1088/1361-6382/acace4

Cited by 14 publications

(6 citation statements)

References 119 publications

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“…As initial data for the head-on simulations we consider a superposition of two PSs with both stars described by the same Proca field following [24,[31][32][33][34][35][36] (see also Refs. [37,38]):…”

Section: B Binary Head-on Datamentioning

confidence: 99%

Impact of the wavelike nature of Proca stars on their gravitational-wave emission

et al. 2022

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We present a systematic study of the dynamics and gravitational-wave emission of head-on collisions of spinning vector boson stars, known as Proca stars. To this aim we build a catalog of about 800 numerical-relativity simulations of such systems. We find that the wavelike nature of bosonic stars has a large impact on the gravitational-wave emission. In particular, we show that the initial relative phase Δϵ ¼ ϵ 1 − ϵ 2 of the two complex fields forming the stars (or, equivalently, the relative phase at merger) strongly impacts both the emitted gravitational-wave energy and the corresponding mode structure. This leads to a nonmonotonic dependence of the emission on the frequency of the secondary star ω 2 , for fixed frequency ω 1 of the primary. This phenomenology, which has not been found for the case of black-hole mergers, reflects the distinct ability of the Proca field to interact with itself in both constructive and destructive manners. We postulate this may serve as a smoking gun to shed light on the possible existence of these objects.

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Section: B Binary Head-on Datamentioning

confidence: 99%

Impact of the wavelike nature of Proca stars on their gravitational-wave emission

et al. 2022

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“…Further BS models include charged stars [44,45], BSs comprised of multi-fields [46,47] and rotating models [48,49], where the nature of the spin is quantised. The stability of various bosonic configurations has been addressed in [50][51][52] and numerous numerical relativity simulations have demonstrated the robustness of the models [36,[53][54][55].…”

Section: Introductionmentioning

confidence: 99%

“…The GW signal generated by the merger remnant is furthermore mainly governed by the fundamental oscillation frequency of the remnant as it settles down into a non-spinning configuration [70]. Quite remarkably, the GW signal from BS binary mergers can be exceptionally long-lived, resulting in a GW afterglow that decays at a much slower rate than the remnant's angular momentum [55]. The inspiral of unequal-mass BS binaries has been studied in [54] and can result in large kicks of thousands of km s −1 which, however, is due to the asymmetric ejection of bosonic matter rather than that of GWs.…”

Section: Introductionmentioning

confidence: 99%

“…In this work, we develop a generalised version of this method that achieves the same benefits for binaries with arbitrary mass ratios and contains the equal-mass fix as a limiting case in the choice of two free parameters. The proposed methodology can be applied to head-on collisions as well as systems with angular momentum, as for example in [55]. Here we employ this improved initial data construction in the simulation of equal-and unequal-mass BS binary head-on collisions studying systematically the impact of the BSs' phase offset on the collision dynamics and resulting GW signals.…”

Section: Introductionmentioning

confidence: 99%

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Unequal-mass boson-star binaries: initial data and merger dynamics

Evstafyeva

Sperhake

Helfer

et al. 2023

Class. Quantum Grav.

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We present a generalization of the curative initial data construction derived for equal-mass compact binaries in Refs.[1,2] to arbitrary mass ratios. We demonstrate how these improved initial data avoid substantial spurious artifacts in the collision dynamics of unequal-mass boson-star binaries in the same way as has previously been achieved with the simpler method restricted to the equal-mass case. We employ the improved initial data to explore in detail the impact of phase offsets in the coalescence of equal- and unequal-mass boson star binaries.

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“…However, only stars in scalar models with self-interactions are perturbatively stable against a non-axisymmetric instability [55][56][57][58]. Lastly, despite numerous efforts to form rotating BSs dynamically [40,[43][44][45]59], even in those models with rotating stars without known instabilities [57], no rotating BSs has been formed from the merger of two non-spinning stars. If BSs mergers cannot form a (nonblack-hole) rotating remnant, that would seem to place a serious impediment on their ability to mimic black holes without invoking horizons.…”

Section: Introductionmentioning

confidence: 99%

Binary boson stars: Merger dynamics and formation of rotating remnant stars

Siemonsen¹,

East²

2023

Preprint

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Scalar boson stars have attracted attention as simple models for exploring the nonlinear dynamics of a large class of ultra compact and black hole mimicking objects. Here, we study the impact of interactions in the scalar matter making up these stars. In particular, we show the pivotal role the scalar phase and vortex structure play during the late inspiral, merger, and post-merger oscillations of a binary boson star, as well as their impact on the properties of the merger remnant. To that end, we construct constraint satisfying binary boson star initial data and numerically evolve the nonlinear set of Einstein-Klein-Gordon equations. We demonstrate that the scalar interactions can significantly affect the inspiral gravitational wave amplitude and phase, and the length of a potential hypermassive phase shortly after merger. If a black hole is formed after merger, we find its spin angular momentum to be consistent with similar binary black hole and binary neutron star merger remnants. Furthermore, we formulate a mapping that approximately predicts the remnant properties of any given binary boson star merger. Guided by this mapping, we use numerical evolutions to explicitly demonstrate, for the first time, that rotating boson stars can form as remnants from the merger of two non-spinning boson stars. We characterize this new formation mechanism and discuss its robustness. Finally, we comment on the implications for rotating Proca stars.

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The gravitational afterglow of boson stars

Cited by 14 publications

References 119 publications

Impact of the wavelike nature of Proca stars on their gravitational-wave emission

Impact of the wavelike nature of Proca stars on their gravitational-wave emission

Unequal-mass boson-star binaries: initial data and merger dynamics

Binary boson stars: Merger dynamics and formation of rotating remnant stars

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