arXiv subjects

Danilo Chiaramello

Publications and source records attributed to Danilo Chiaramello.

9 recordsLinked to original sources

arXiv2026

Gravitational Wave Hyperbolic Catalog: Reanalyzing High-Mass Gravitational Wave Signals Using Hyperbolic Waveforms

Close hyperbolic encounters between black holes produce distinctive bursts of gravitational radiation with a time-frequency morphology that is qualitatively different from that of quasi-circular inspirals. Expected to arise in dense stellar environments through dynamical interactions, these encounters probe formation channels and mass ranges inaccessible to isolated binary evolution, making them a compelling target for current and next-generation detectors. In this work, we reanalyze \totalevents high-mass events from the LIGO-Virgo-KAGRA catalogs using the hyperbolic configuration of the~\dali~waveform model. We compare these with analyses using the quasi-circular, precessing configuration of the same model, computing Bayes factors to evaluate which description is favored by the data. We find that most events strongly to mildly favor the quasi-circular, precessing scenario, except for GW190521. For this event, we find that the signal is best fit by a dynamical capture waveform, with Bayes factor $\ln \mathcal{B}^{\rm hyp}_{\rm prec}=3.71^{+0.11}_{-0.11}$. We confirm this preference via further analyses with~\dali~in different configurations (quasi-circular, non-precessing; eccentric, non-precessing; and eccentric, precessing), as well as one using the quasi-circular, precessing numerical relativity surrogate model \nrsur. We also highlight the results we obtain for GW231123, another high-mass signal linked to evidence of strong precession, for which we find strong preference for the quasi-circular, precessing scenario, with $\ln \mathcal{B}^{\rm hyp}_{\rm prec}=-15.80^{+0.24}_{-0.24}$. The analysis of mock signals generated with the best fitting waveforms for GW190521 and GW231123 suggest that the former might belong to a region of parameter space where high-mass, bound, precessing signals can be hard to distinguish from dynamical captures in parameter estimation.

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arXiv2026

Spin the black circle II: tidal heating and torquing of a rotating black hole by a test mass on generic orbits

Horizon fluxes of energy and angular momentum are a key strong-field effect in the dynamics of black holes, encoding direct information about their nature. In this work, we present a numerical study of these fluxes for a test particle orbiting a Kerr black hole on equatorial geodesics, covering circular, eccentric, and hyperbolic trajectories across a wide range of orbital parameters and black hole spins. We reproduce known results for circular orbits and uncover a richer phenomenology for eccentric and hyperbolic ones: the instantaneous fluxes can exhibit multiple peaks and sign changes, indicating a complex interplay between superradiant and non-superradiant regimes. We then compare these results against existing analytical post-Newtonian expressions, exploring resummation strategies to improve their performance against numerical data. In particular, we propose a factorized and resummed representation of the horizon fluxes that predicts the onset frequency of the superradiant regime to within $10\%$ for $\gtrsim 73\%$ of configurations for both the energy and angular momentum fluxes. This representation exactly reduces to the circular limit by construction, independently of the perturbative order of the remaining analytical terms. For peak and orbit-averaged fluxes, the analytical models achieve acceptable accuracy -- with relative errors at the $10\%$ level or below -- at large separations and low eccentricities. However, they can exhibit deviations of $\sim \mathcal{O}(100\%)$ in the strong-field regime, motivating the need for improved flux prescriptions and further investigations.

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arXiv2026

From Source Properties to Strong-Field Tests: a multipronged analysis of GW250114 with an effective one-body model for generic orbits

We present a detailed analysis of GW250114, the loudest gravitational-wave signal observed to date, using a waveform model capable of describing binary black holes in generic (eccentric and precessing) orbits. Our analysis builds on LIGO-Virgo-KAGRA (LVK)'s results, finding that the source is consistent at a probability of $\geq 96\%$ with the merger of two first-generation, nearly equal-mass, low-spin black holes, forming a remnant within the pair-instability mass gap. The signal's high signal-to-noise ratio ($\gtrsim 75$) enables the detection of the subdominant $(4,\pm4)$ multipoles, whose presence we confirm with higher evidence than previously reported by the LVK. Restricting the analysis even to post-peak data yields $\log_{10}B\gtrsim 1$ in favor of models including the $(4,\pm4)$ mode, demonstrating that this contribution remains detectable well into the post-merger phase. We further perform three independent tests of general relativity, complementary to those performed by the LVK: a modified residual analysis confirms that our semi-analytical model fully describes the signal without detectable discrepancies; a subdominant mode test finds that the amplitude of the $(4,\pm4)$ multipoles agrees with general-relativistic expectations; and a parameterised analysis of the plunge-merger-ringdown regime recovers the GR expectation within the 50\% credible region for the remnant mass and spin, and within the 90\% interval for the $(2,\pm2)$ peak amplitude. Collectively, these results reinforce GW250114 as a landmark event for a precision test of gravity.

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arXiv2025

A parametrized model for gravitational waves from eccentric, precessing binary black holes: theory-agnostic tests of General Relativity with pTEOBResumS

Gravitational waves from binary black hole (BBH) mergers allow us to test general relativity in the strong-field, high-curvature regime. However, existing gravitational wave-based tests have so far assumed non-eccentric signal sources, limiting their applicability to more general astrophysical scenarios. In this work, we present pTEOBResumS, a new parametrized inspiral-merger-ringdown model for null tests of GR that incorporates both orbital eccentricity and spin precession. Building on the effective-one-body model TEOBResumS-Dalí, we introduce parametrized deviations from GR both in the inspiral and the merger-ringdown regimes. We validate the model via parameter estimation of synthetic signals, including from numerical relativity simulations of BBHs and a boson star binary. These allow us to establish the model's consistency, demonstrate its capability to identify beyond-GR effects, and gauge the impact of eccentricity in tests of GR. We then analyze a set of BBH events from the first three LIGO-Virgo-KAGRA observing runs, testing whether they are best explained by a GR or non-GR waveform, under either the eccentric, spin-aligned or precessing, quasi-circular hypotheses. We find no significant statistical evidence in favor of deviations from GR. Consistent with previous works, we infer a mild preference for longer remnant quasi-normal mode damping times than expected in GR, though the limited sample and potential systematics reduce its significance. In addition, when weighting by signal strength, joint posteriors combining the individual events are still compatible with GR. We find no strong evidence for imprints of orbital eccentricity in the analyzed events, with the exception of GW200129. For this, our analysis finds a strong preference for an eccentric, GR-consistent description, although as previous works have noted this result could be influenced by data quality issues.

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arXiv2025

Revisiting GW150914 with a non-planar, eccentric waveform model

The first direct detection of gravitational waves by the LIGO collaboration, GW150914, marked the start of a new exciting era in astronomy, enabling the study of the Universe through a new messenger. Since then, the field has grown rapidly, with the development of increasingly more sophisticated techniques to detect, analyze and interpret the signals. In this paper we revisit GW150914, presenting updated estimates of its source parameters using a waveform model developed within the EOB formalism, able to describe gravitational-wave emission from generic non-circular, non-planar binaries. We provide a comprehensive analysis of the signal and its properties, considering and contrasting various scenarios for the source: from the simplest, aligned-spin quasi-circular binary black hole merger, to more complex scenarios, including precession, eccentricity or both. Unsurprisingly, we find that the signal is consistent with a quasi-circular ($e < 0.08$ at $15$ Hz), slowly spinning $(χ_{\rm eff} = -0.03^{+0.12}_{-0.13})$ binary black hole merger, a-posteriori validating a considerable body of works. This is the first analysis performed with an inspiral-merger-ringdown model containing both eccentricity and precession.

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arXiv2025

Effective-one-body waveform model for noncircularized, planar, coalescing black hole binaries II:high accuracy by improving logarithmic terms in resummations

Effective-one-body (EOB) models are based on analytical building blocks that, mathematically, are truncated Taylor series with logarithms. These functions are usually resummed using Padé approximants obtained first assuming that the logarithms are constant, and then replacing them back into the resulting rational functions. A recent study pointed out that this procedure introduces spurious logarithmic terms when the resummed functions are reexpanded. Here we update the TEOBResumS-Dalí waveform model for spin-aligned, noncircularized coalescing black hole binaries by systematically implementing new (still Padé based) resummations for all EOB functions (that is, the metric potentials $A, D$ and the residual waveform amplitude corrections $ρ_{\ell m}$ up to $\ell=8$). Once the model is informed by 50 Numerical Relativity simulations, this new approach proves key in lowering the maximum EOB/NR unfaithfulness $\bar{F}_{\rm EOBNR}^{\rm max}$ for the $\ell=m=2$ mode (with the Advanced LIGO noise in the total mass range $10-200M_{\odot}$) over 530 spin-aligned waveforms of the Simulating eXtreme Spacetimes catalog. A median unfaithfulness equal to $3.09\times 10^{-4}$ is achieved, which is a marked improvement over the previous value, $1.06\times 10^{-3}$. The largest value, ${\rm Max}[\bar{F}^{\rm max}_{\rm EOBNR}]= 6.80\times 10^{-3}$, is found for an equal-mass, equal-spin simulation with dimensionless spins $\sim +0.998$; only five configurations have $\bar{F}^{\rm max}_{\rm EOBNR} > 5\times 10^{-3}$ (four of which equal-mass and with equal spins larger than $\sim +0.98$). Results for eccentric binaries are similarly excellent (well below $10^{-2}$ and mostly around $10^{-3}$).

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arXiv2024

Spin the black circle: horizon absorption on non-circular, planar binary black hole dynamics

Binary systems of black holes emit gravitational waves as they move through their orbits. While most of the emitted radiation escapes to future null infinity, a small fraction is absorbed by the black holes themselves. This is known as horizon absorption or tidal heating/torquing, and causes the black holes' masses and spins to change as the system evolves. In this work, we quantify the effects of the horizon fluxes on binary black hole dynamics by computing them up to next-to-next-to-leading order on generic planar orbits, also exploring physically motivated factorizations of the results. We integrate these fluxes over unbound, hyperbolic-like trajectories obtained with the Effective-One-Body model TEOBResumS-Dalí. We discuss the resulting phenomenology across a sizable slice of the relevant parameter space, finding a very small effect in most cases, except on highly energetic orbits. However, the predicted mass and spin variations are quantitatively and qualitatively very sensitive to the analytical representation chosen for the fluxes in that regime. We then perform comparisons with numerical relativity data of induced spins from hyperbolic encounters of initially nonrotating black holes, finding that the next-to-next-to-leading order factorized expressions we derive are crucial to reproduce the data. An optimization on the initial conditions (energy, angular momentum) is necessary for this, however, with differences of up to 9% between the numerical and optimal initial data. Finally, we use our analytical expressions to model possible astrophysical implications for black holes in globular clusters.

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arXiv2024

Towards efficient Effective One Body models for generic, non-planar orbits

Complete waveform models able to account for arbitrary non-planar orbits represent a holy grail in current gravitational-wave astronomy. Here, we take a step towards this direction and present a simple yet efficient prescription to obtain the evolution of the spin vectors and of the orbital angular momentum along non-circularized orbits, that can be applied to any eccentric aligned-spins waveform model. The scheme employed is motivated by insights gained from the post-Newtonian (PN) regime. We investigate the phenomenology of the Euler angles characterizing the time-dependent rotation that connects the co-precessing frame to the inertial one, gauging the importance of non-circular terms in the evolution of the spins of a precessing binary. We demonstrate that such terms are largely negligible, irrespectively of the details of the orbit. Such insights are confirmed by studying the radiation-frame of a few eccentric, precessing numerical relativity (NR) simulations. Our investigations confirm that the usual "twisting" technique employed for quasi-spherical systems can be safely applied to non-circularized binaries. By then augmenting a state-of-the-art Effective-One-Body (EOB) model for non-circular planar orbits with the prescription discussed, we obtain an inspiral-merger-ringdown (IMR) model for eccentric, precessing binary black holes (BBHs). We validate the model in the quasi-spherical limit via mismatches and present one phasing comparison against a precessing, eccentric simulation from the RIT catalog.

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arXiv2020

A faithful analytical effective one body waveform model for spin-aligned, moderately eccentric, coalescing black hole binaries

We present a new effective-one-body (EOB) model for eccentric binary coalescences. The model stems from the state-of-the-art model TEOBResumS$\_$SM for circularized coalescing black-hole binaries, that is modified to explicitly incorporate eccentricity effects both in the radiation reaction and in the waveform. Using Regge-Wheeler-Zerilli type calculations of the gravitational wave losses as benchmarks, we find that a rather accurate ($\sim 1\%$) expression for the radiation reaction along mildly eccentric orbits ($e \sim 0.3$) is given by dressing the current, EOB-resummed, circularized angular momentum flux, with a leading-order (Newtonian-like) prefactor valid along general orbits. An analogous approach is implemented for the waveform multipoles. The model is then completed by the usual merger-ringdown part informed by circularized numerical relativity (NR) simulations. The model is validated against the 22, publicly available, NR simulations calculated by the Simulating eXtreme Spacetime (SXS) collaboration, with mild eccentricities, mass ratios between 1 and 3 and up to rather large dimensionless spin values ($\pm 0.7$). The maximum maximum EOB/NR unfaithfulness, calculated with Advanced LIGO noise, is at most of order $3\%$. The analytical framework presented here should be seen as a promising starting point for developing highly-faithful waveform templates driven by eccentric dynamics for present, and possibly future, gravitational wave detectors.

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