arXiv subjects

Francisco Duque

Publications and source records attributed to Francisco Duque.

At least 19 recordsLinked to original sources

arXiv2026

Gotta light? Illuminating AGN disks with LISA EMRIs

We study the ability of the upcoming Laser Interferometer Space Antenna (LISA) to constrain gas torques acting on extreme-mass-ratio inspirals (EMRIs) when these are embedded in accretion disks, using recently developed relativistic models for the binary-disk interaction. Using a fully Bayesian setup, we find that, contrary to previous forecasts based on Newtonian results, these observations can provide simultaneous estimates of the disk surface density and the accretion rate (or, equivalently, its total luminosity) without the need for an electromagnetic counterpart. Our analysis also indicates that simpler measurement constraints based on the linear-signal (Fisher matrix) approximation are not valid for these systems. For typical EMRI observations, the torque amplitude can be constrained to within ~10%, strengthening the prospect of probing accretion physics at (sub)microparsec scales, deep in the strong-field gravity regime and complementing electromagnetic observations. This also strengthens LISA's ability to help answering questions such as how massive black holes grow and coevolve with their host galaxies and, by helping to identify the EMRI's host galaxy through cross-correlation with AGN catalogues, to improve the use of these sources as (dark) sirens for cosmology.

gr-qc↗

arXiv2026

Quantifying the Scientific Potential of Intermediate and Extreme Mass Ratio Inspirals with the Laser Interferometer Space Antenna

The Laser Interferometer Space Antenna (LISA) will enable precision studies of Extreme and Intermediate Mass Ratio Inspirals (EMRIs/IMRIs), providing unique probes of astrophysical environments of galactic nuclei and strong-field gravity. Using a fully relativistic pipeline across primary masses $m_1 \in [5\times10^4, 10^7]\,M_\odot$ and secondary masses $m_2 \in [1, 10^4]\,M_\odot$, we map instrumental performance directly to detection horizons and parameter measurement precision. EMRIs with $m_1 = 10^7\,M_\odot$ and $m_2 \sim 1\,M_\odot$ are the most sensitive to instrument degradation, with redshift horizons at $z \sim 0.01$, while IMRIs are the least sensitive to degradation and reach redshifts $z \sim 1-3$. All prograde systems considered achieve sub-percent spin precision within three months of observation. The full 4.5-year mission increases the horizon of systems with $m_1 = 10^7\,M_\odot$ and $m_2 \sim 1\,M_\odot$ by a factor of $\sim 4$ and improves sky localization by one to two orders of magnitude reaching $ < 10\,\mathrm{deg}^2$. IMRI detection is robust against degradation, but their parameter estimation is more vulnerable due to fewer cycles in band. With the full baseline, EMRI observations constrain scalar dipole emission and Kerr quadrupole deviations below ground-based bounds by one to two orders of magnitude. We release the accompanying software and an interactive website to enable the community to rapidly quantify the scientific potential of EMRIs and IMRIs.

astro-ph.IM↗

arXiv2025

Gravitational Atom Spectroscopy

Black holes in our Universe are rarely truly isolated, being instead embedded in astrophysical environments such as plasma or dark matter. A particularly intriguing possibility is that light scalar fields form bound states around black holes, producing extended ''clouds'' known as gravitational atoms. When these clouds become sufficiently compact, the spacetime can no longer be described by a vacuum solution of General Relativity. In this regime, one can construct quasi-stationary, spherically symmetric, self-gravitating scalar gravitational-atom configurations. Here, we explore an observationally relevant aspect of these systems by computing their fundamental quasi-normal mode. We present a fully relativistic calculation of the axial modes in both the time and frequency domains, finding frequency shifts relative to the vacuum case that depends mostly on the compactness of the gravitational atom. For sufficiently compact configurations, these shifts may be detectable by current or future gravitational wave detectors.

gr-qc↗

arXiv2025

Extreme-mass-ratio inspirals in relativistic accretion discs

We compute relativistic Lindblad torques for circular, equatorial extreme-mass-ratio inspirals (EMRIs) embedded in relativistic thin accretion discs, including spinning black hole configurations. We find that relativistic effects can amplify the magnitude of these torques by orders of magnitude in the strong-field regime, and that the torque can even reverse direction as the EMRI approaches the innermost stable circular orbit (ISCO). However, we show that the location of this reversal is highly spin-dependent, shifting progressively closer to the ISCO, where gravitational-wave emission completely dominates the inspiral, as the spin of the central black hole increases. Spin also modifies the radial dependence of the Lindblad torques. We investigate whether Lindblad torques can be approximated by parametrised power laws of the form T_LR = A(r_s / 10M)^n_r (or combinations thereof), and find significant spin- and disc-dependent variations in the slope parameter n_r. For instance, for spin a/M = 0.9, we find n_r = 3.6 in the strong-field regime, compared to the Newtonian value of n_r = 4.5. Given current forecasts of parameter recovery for ``golden'', loud EMRIs in accretion discs (\Delta n_r ~ 0.5), we predict LISA could distinguish between different disc configurations through their relativistic Lindblad torque signatures, providing the first direct probe of the midplane structure of the inner region of accretion discs, which is inaccessible to electromagnetic observations.

gr-qc↗

arXiv2025

Prospects for EMRI/MBH parameter estimation using Quasi-Periodic Eruption timings: short-timescale analysis

Quasi-Periodic Eruptions (QPEs) are luminous, recurring X-ray outbursts from galactic nuclei, with timescales of hours to days. While their origin remains uncertain, leading models invoke accretion disk instabilities or the interaction of a massive black hole (MBH) with a lower-mass secondary in an extreme mass ratio inspiral (EMRI). EMRI scenarios offer a robust framework for interpreting QPEs by characterizing observational signatures associated with the secondary's orbital dynamics. This, in turn, enables extraction of the MBH/EMRI physical properties and provides a means to test the EMRI scenario, distinguishing models and addressing the question: what can QPE timings teach us about massive black holes and EMRIs? In this study, we employ analytic expressions for Kerr geodesics to efficiently resolve the trajectory of the secondary object and perform GPU-accelerated Bayesian inference to assess the information content of QPE timings. Using our inference framework, referred to as QPE-FIT (Fast Inference with Timing), we explore QPE timing constraints on astrophysical parameters, such as EMRI orbital parameters and MBH mass/spin. We find that mild-eccentricity EMRIs ($e\sim0.1-0.3$) can constrain MBH mass and EMRI semimajor axis/eccentricity to the 10% level within tens of orbital periods, while MBH spin is unconstrained for the explored semimajor axes $\geq 100R_g$ and monitoring baselines $\mathcal{O}(10-100\rm)$ orbits. Introducing a misaligned precessing disk generally degrades inference of EMRI orbital parameters, but can constrain disk precession properties within 10-50%. This work both highlights the prospect of QPE observations as dynamical probes of galactic nuclei and outlines the challenge of doing so in the multimodal parameter space of EMRI-disk collisions.

astro-ph.HE↗

arXiv2025

Gravitational-wave tails and memory effect for mergers in astrophysical environments

Gravitational waves from the coalescence of compact objects carry information about their dynamics and the spacetime in regions where they are evolving. In particular, late-time tails and memory effects after the merger are two low-frequency phenomena, not detectable by current instruments, but which can be observed by future detectors. Their low-frequency nature could, in principle, make them more sensitive to larger-scale structures at galactic length scales. We show that indeed there are transient features, such as amplitude changes, in both tails and (linear) memory when the merger occurs while immersed in an astrophysical environment. For realistic galaxies, the environment's compactness is small enough that the effect is strongly suppressed, but these effects could become relevant for mergers occurring in regions with matter overdensities, like the ones recently observed numerically for wave dark matter. On the other hand, the memory (the difference between the amplitude asymptotically early and late) and asymptotically late decay are independent on the properties of the environment.

gr-qc↗

arXiv2025

Black hole spectroscopy: from theory to experiment

The "ringdown" radiation emitted by oscillating black holes has great scientific potential. By carefully predicting the frequencies and amplitudes of black hole quasinormal modes and comparing them with gravitational-wave data from compact binary mergers we can advance our understanding of the two-body problem in general relativity, verify the predictions of the theory in the regime of strong and dynamical gravitational fields, and search for physics beyond the Standard Model or new gravitational degrees of freedom. We summarize the state of the art in our understanding of black hole quasinormal modes in general relativity and modified gravity, their excitation, and the modeling of ringdown waveforms. We also review the status of LIGO-Virgo-KAGRA ringdown observations, data analysis techniques, and the bright prospects of the field in the era of LISA and next-generation ground-based gravitational-wave detectors.

gr-qc↗

arXiv2025

Bias-Corrected Importance Sampling for Inferring Beyond-Vacuum-GR Effects in Gravitational-Wave Sources

The upcoming gravitational wave (GW) observatory LISA will measure the parameters of sources like extreme-mass-ratio inspirals (EMRIs) to exquisite precision. These measurements will also be sensitive to perturbations to the vacuum, GR-consistent evolution of sources, which might be caused by astrophysical environments or deviations from general relativity (GR). Previous studies have shown such ``beyond-vacuum-GR'' perturbations to potentially induce severe biases ($\gtrsim 10\sigma$) on recovered parameters under the ``null'' vacuum-GR hypothesis. While Bayesian inference can be performed under the null hypothesis using Markov Chain Monte Carlo (MCMC) samplers, it is computationally infeasible to repeat for more than a modest subset of all possible beyond-vacuum-GR hypotheses. We introduce bias-corrected importance sampling, a generic inference technique for nested models that is informed by the null hypothesis posteriors and the linear signal approximation to correct any induced inference biases. For a typical EMRI source that is significantly influenced by its environment but has been inferred only under the null hypothesis, the proposed method efficiently recovers the injected (unbiased) source parameters and the true posterior at a fraction of the expense of redoing MCMC inference under the full hypothesis. In future GW data analysis using the output of the proposed LISA global-fit pipeline, such methods may be necessary for the feasible and systematic inference of beyond-vacuum-GR effects.

gr-qc↗

arXiv2025

Black hole spectroscopy in environments: detectability prospects

The ringdown phase following a binary black hole coalescence is a powerful tool for measuring properties of the remnant black hole. Future gravitational wave detectors will increase the precision of these measurements and may be sensitive to the environment surrounding the black hole. This work examines how environments affect the ringdown from a binary coalescence. Our analysis shows that for astrophysical parameters and sensitivity of planned detectors, the ringdown signal is indistinguishable from its vacuum counterpart, suggesting that ringdown-only analyses can reliably extract the (redshifted) mass and spin of the remnant black hole. These conclusions include models with spectral instabilities, suggesting that these are not relevant from an observational viewpoint. Deviations from inspiral-only estimates could then enhance the characterisation of environmental effects present during the coalescence.

gr-qc↗

arXiv2025

Gravitational Waves from Accretion Disks: Turbulence, Mode Excitation and Prospects for Future Detectors

We study gravitational-wave emission by turbulent flows in accretion disks around spinning black holes or neutron stars. We aim to understand how turbulence can stochastically excite black hole quasinormal ringing and contribute to a stochastic gravitational-wave background from accretion disks around compact objects. We employ general relativistic magnetohydrodynamic simulations and feed them as the source of the Teukolsky master equation to evaluate the gravitational wave energy spectrum of a single source. The stochastic gravitational wave background from accretion disks generated by the population of stellar-mass compact objects is far below the sensitivity of third-generation ground-based detectors. In contrast, the supermassive black hole population, in particular those actively accreting, could lead to $Ω_{\mathrm{GW}}\sim 10^{-15}$ in the microHertz. This signal remains well below the sensitivities of pulsar-timing-arrays and LISA, making direct observation infeasible.

gr-qc↗

arXiv2025

Constraining accretion physics with gravitational waves from eccentric extreme-mass-ratio inspirals

We study the evolution of eccentric, equatorial extreme-mass-ratio inspirals (EMRIs) immersed in the accretion disks of active galactic nuclei. We find that single gravitational-wave observations from these systems could provide measurements with ~ 10 % relative precision of, simultaneously, the disk viscosity and mass accretion rate of the central supermassive black hole. This is possible when the EMRI transitions, within the observation time, from supersonic to subsonic motion relative to the disk gas, for eccentricities e > ~ 0.025-0.1. The estimate of the accretion rate would assist in the identification of the EMRI's host galaxy, or the observation of a direct electromagnetic counterpart, improving the chances of using these sources as cosmological sirens. Our work highlights the rich phenomenology of binary evolution in astrophysical environments and the need to improve the modelling and analysis of these systems for future gravitational-wave astronomy.

gr-qc↗

arXiv2024

New Horizons for Psi: Extreme-Mass-Ratio Inspirals in Fundamental Fields

This set of notes guided a 2 hour lecture on "Extreme-Mass-Ratio Inspirals in Fundamental Fields for the New Horizons for Psi School and Workshop", hosted at Instituto Superior Tecnico, University of Lisbon, between 1 - 5 July 2024. It introduces how to model asymmetric mass-ratio binaries evolving while immersed in an environment constituted by an ultralight (complex) scalar field using techniques of black hole perturbation theory, and focusing on the simpler example of a spherically symmetric cloud around a non-rotating black hole. A Mathematica notebook with the derivation and solver of the equations of motion of the system is also provided.

gr-qc↗

arXiv2024

Systematics in tests of general relativity using LISA massive black hole binaries

Our current understanding is that an environment - mainly consisting of gas or stars - is required to bring massive black hole binaries (MBHBs) with total redshifted mass $M_z\sim[10^{4},10^7]~{\rm M}_\odot$ to the LISA band from parsec separation. Even in the gravitational wave (GW) dominated final inspiral, realistic environments can non-negligibly speed up or slow down the binary evolution, or leave residual, measurable eccentricity in the LISA band. Despite this fact, most of the literature does not consider environmental effects or orbital eccentricity in modelling GWs from near-equal mass MBHBs. Considering either a circular MBHB embedded in a circumbinary disc or a vacuum eccentric binary, we explore if ignoring either secular gas effects (migration and accretion) or eccentric corrections to the GW waveform can mimic a failure of General Relativity (GR). We use inspiral-only aligned-spin 3.5 post-Newtonian waveforms, a complete LISA response model, and Bayesian inference to perform a parameterized test of GR. For a four-year LISA observation of an MBHB with $M_z=10^{5}~{\rm M}_\odot$, primary-to-secondary mass ratio $q=8$, and component BHs' dimensionless spins $χ_{1,2}=0.9$ at redshift $z=1$, even a moderate gas-disc imprint (Eddington ratio ${\rm f}_{\rm Edd}\sim0.1$) or low initial eccentricity ($e_0\sim10^{-2.5}$) causes a false violation of GR in several PN orders. However, correctly modelling either effect can mitigate systematics while avoiding significant biases in vacuum circular systems. The adoption of LISA makes it urgent to consider gas imprints and eccentricity in waveform models to ensure accurate inference for MBHBs.

astro-ph.GA↗

arXiv2024

Impact of relativistic waveforms in LISA's science objectives with extreme-mass-ratio inspirals

Extreme-Mass-Ratio Inspirals (EMRIs) are one of the key targets for future space-based gravitational wave detectors, such as LISA. The scientific potential of these sources can only be fully realized with fast and accurate waveform models. In this work, we extend the \textsc{FastEMRIWaveform} (\texttt{FEW}) framework by providing fully relativistic waveforms at adiabatic order for circular, equatorial orbits in Kerr spacetime, for mass ratios up to $10^{-3}$. We investigate the significance of including relativistic corrections in the waveform for both vacuum and non-vacuum environments. Specifically, we develop relativistic non-vacuum EMRI waveforms including two different environmental effects in the EMRI waveforms: power-law migration torques, and superradiance scalar clouds. For EMRIs in vacuum, we find that non-relativistic waveforms incorrectly estimate the predicted source's horizon redshift by approximately $35\%$ error. Our analysis shows that incorporating relativistic corrections enhances constraints on accretion disks, modeled through power-law torques, and improves the constraints on disk parameter estimates (error $\simeq 8\%$), representing a significant improvement over previous estimates. Additionally, we assess the evidence for models in a scenario where ignoring the accretion disk biases the parameter estimation (PE), reporting a $\log_{10}$ Bayes factor of $1.1$ in favor of the accretion disk model. In a fully relativistic setup, we also estimate the parameters of superradiant scalar clouds with relative errors $\simeq 0.3\%$ for the scalar cloud's mass. These results demonstrate that incorporating relativistic effects is essential for LISA science objectives with EMRIs.

gr-qc↗

arXiv2024

Extreme mass-ratio inspirals in ultra-light dark matter

Previous works have argued that future gravitational-wave detectors will be able to probe the properties of astrophysical environments where binary coalesce, including accretion disks, but also dark matter structures. Most analyses have resorted to a Newtonian modelling of the environmental effects, which are not suited to study extreme-mass-ratio inspirals immersed in structures of ultra-light bosons. In this letter, we use relativistic perturbation theory to consistently study these systems in spherical symmetry. We compute the flux of scalar particles and the rate at which orbital energy (and angular momentum) is dissipated via gravitational radiation and depletion of scalars, i.e. dynamical friction. Our results suggest that the Laser Inteferometer Space Antenna will be able to probe ultra-light dark matter structures in the Galaxy by tracking the phase of extreme-mass-ratio inspirals.

gr-qc↗

arXiv2024

Black-hole spectroscopy: quasinormal modes, ringdown stability and the pseudospectrum

Black-hole spectroscopy is a powerful tool to probe the Kerr nature of astrophysical compact objects and their environment. The observation of multiple ringdown modes in gravitational waveforms could soon lead to high-precision gravitational-wave spectroscopy, thus it is critical to understand if the quasinormal mode spectrum itself is affected by astrophysical environments, quantum corrections, and other generic modifications. In this chapter, we will review the black-hole spectroscopy program and its challenges regarding quasinormal mode detection, the overtone status and the recent evidence that supports the existence of nonlinearities in the spectrum of black holes. We will then discuss a newly introduced non-modal tool in black-hole physics, namely the pseudospectrum; a mathematical notion that can shed light on the spectral stability of quasinormal modes, and discuss its novel applications in black holes and exotic horizonless compact objects. We will show that quasinormal modes generically suffer from spectral instabilities, explore how such phenomena can further affect black-hole spectroscopy, and discuss potential ringdown imprints and waveform stability issues in current and future gravitational-wave detectors.

gr-qc↗

arXiv2024

Hushing black holes: tails in dynamical spacetimes

Stationary, asymptotically flat, black hole solutions of the vacuum field equations of General Relativity belong to the Kerr family. But how does one approach this state, dynamically? Linearized fluctuations decay at late times, at fixed spatial position, as a Price power law for generic initial conditions. However, little attention was paid to forced and nonlinear spacetimes, where matter and nonlinearities play a role. We uncover a new, source-driven tail governing waves generated by pointlike matter and nonlinearities, which can dominate over Price's decay.

gr-qc↗

arXiv2023

Constraints on massive gravity from dipolar mode excitations

We study extreme-mass-ratio systems in theories admitting the Schwarzschild solution and propagating a massive graviton. We show that, in addition to small corrections to the quadrupolar and higher-order modes, a dipolar mode is excited in these theories and we quantify its excitation. While LIGO-Virgo-KAGRA observations are not expected to impose meaningful constraints in the dipolar sector, future observations by the Einstein Telescope or by LISA, together with bounds from dispersion relations, can rule out theories of massive gravity admitting vacuum General Relativistic backgrounds. For the bound to be circumvented, one needs to move away from Ricci-flat solutions, and enter a territory where constraints based on wave propagation and dispersion relations are not reliable.

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