arXiv subjects

Massimo Vaglio

Publications and source records attributed to Massimo Vaglio.

9 recordsLinked to original sources

arXiv2026

Constraints on Einstein-aether gravity from the precision timing of PSR J1738+0333

We constrain Einstein-aether gravity -- a Lorentz-violating extension of General Relativity in which a dynamical, unit timelike vector field selects a preferred frame -- using updated high-precision pulsar timing observations of PSR J1738+0333 from EPTA second Data Release and the NANOGrav 9-year release, in combination with ToAs from Arecibo, Green Bank, Nancay, Parkes, and Westerbork. Our method accounts for both conservative and dissipative first post-Newtonian corrections arising from Lorentz violation; here we apply it to PSR J1738+0333 using the Bayesian timing pipeline Vela to process the full ToA dataset. We sample the joint posterior over binary component masses, post-Keplerian parameters and center-of-mass velocity components, and then apply a resampling scheme to propagate posteriors into robust constraints on the fundamental theory parameters, obtaining the most stringent strong-field bounds on the Einstein-aether coupling constants from a single binary pulsar system to date.

gr-qc↗

arXiv2026

Looking for non-gaussianity in Pulsar Timing Arrays through the four point correlator

Pulsar Timing Arrays have recently reported strong evidence for a stochastic gravitational wave background. In standard analyses, it is modeled through pulsar-dependent Fourier coefficients assumed to follow gaussian statistics, so that the signal is fully characterized by its two-point function. However, if the background arises from a finite population of inspiralling supermassive black hole binaries, non-gaussian features may emerge, making the determination of higher-order correlators essential. In this work, we compute the complete four-point correlator of the stochastic gravitational wave background Fourier coefficients for four arbitrary pulsar positions, identifying it as the leading probe of non-gaussianity. The result separates into a gaussian contribution, proportional to the square of the two-point function, and a genuinely non-gaussian connected component, whose non-trivial angular dependence generalizes the Hellings and Downs correlation to four pulsars. This angular structure depends only on averages of products of antenna pattern functions, and is therefore expected to be independent of the specific physical origin of the background. We further propose to incorporate the four-point correlator into the parameter-estimation pipeline by deriving a marginalized likelihood that perturbatively accounts for non-gaussian effects. Our results provide the theoretical framework to search for non-gaussian features in pulsar timing array data, opening the way to a more complete characterization of gravitational-wave backgrounds.

gr-qc↗

arXiv2025

Searching for Gravitational Waves with Gaia and its Cross-Correlation with PTA: Absolute vs Relative Astrometry

Astrometric missions like Gaia provide exceptionally precise measurements of stellar positions and proper motions. Gravitational waves traveling between the observer and distant stars can induce small, correlated shifts in these apparent positions, a phenomenon known as astrometric deflection. The precision and scale of astrometric datasets make them well-suited for searching for a stochastic gravitational wave background, whose signature appears in the two-point correlation function of the deflection field across the sky. Although Gaia achieves high accuracy in measuring angular separations in its focal plane, systematic uncertainties in the satellite's absolute orientation limit the precision of absolute position measurements. These orientation errors can be mitigated by focusing on relative angles between star pairs, which effectively cancel out common-mode orientation noise. In this work, we compute the astrometric response and the overlap reduction functions for this relative astrometry approach, correcting previous expressions presented in the literature. We use a Fisher matrix analysis to compare the sensitivity of relative astrometry to that of conventional absolute astrometry. Our analysis shows that while the relative method is theoretically sound, its sensitivity is limited for closely spaced star pairs within a single Gaia field of view. Pairs with large angular separations could provide competitive sensitivity, but are practically inaccessible due to Gaia's scanning law. Finally, we demonstrate that combining astrometric data with observations from pulsar timing arrays leads to slight improvements in sensitivity at frequencies greater than approximately 10^-7 Hz.

gr-qc↗

arXiv2025

Systematic bias in LISA ringdown analysis due to waveform inaccuracy

Inaccurate modeling of gravitational-wave signals can introduce systematic biases in the inferred source parameters. As detector sensitivities improve and signals become louder, mitigating such waveform-induced systematics becomes increasingly important. In this work, we assess the systematic biases introduced by an incomplete description of the ringdown signal from massive black hole binaries in the LISA band. Specifically, we investigate the impact of mode truncation in the ringdown template. Using a reference waveform composed of 13 modes, we establish a mode hierarchy and determine the minimum number of modes required to avoid parameter biases across a wide range of LISA sources. For typical systems with masses $\sim 10^6$--$10^7\,M_\odot$ at redshifts $z \sim 2$--$6$, we find that at least 3--6 modes are needed for accurate parameter estimation, while high-SNR events may need at least 10 modes. Our results are a window-insensitive lower bound on the minimum number of modes, as more modes may be needed depending on the choice of time-domain windowing of the post-merger signal.

gr-qc↗

arXiv2024

Cosmology and nuclear-physics implications of a subsolar gravitational-wave event

Detecting a compact subsolar object would have profound implications in physics, the reach of which depends on the nature of the object. Here we explore such consequences for a putative subsolar-mass gravitational wave event detected by the LIGO-Virgo-KAGRA Collaboration. We forecast that the nature of a subsolar binary (made of light neutron stars, primordial black holes, or more exotic compact objects) can be inferred with a great statistical confidence level already during the ongoing fourth observing run, based on the large tidal deformability effects on the signal. The detection of a primordial black hole would have implications for cosmology and dark matter scenarios, while the measurement of the tidal deformability of a subsolar neutron star could rule out or confirm the existence of strange stars made of quarks.

astro-ph.HE↗

arXiv2023

Extreme-mass-ratio inspirals into rotating boson stars: nonintegrability, chaos, and transient resonances

General relativity predicts that black holes are described by the Kerr metric, which has integrable geodesics. This property is crucial to produce accurate waveforms from extreme-mass-ratio inspirals. Astrophysical environments, modifications of gravity and new fundamental fields may lead to nonintegrable geodesics, inducing chaotic effects. We study geodesics around self-interacting rotating boson stars and find robust evidence of nonintegrability and chaos. We identify islands of stability around resonant orbits, where the orbital radial and polar oscillation frequency ratios, known as rotation numbers, remain constant throughout the island. These islands are generically present both in the exterior and the interior of compact boson stars. A monotonicity change of rotation curves takes place as orbits travel from the exterior to the interior of the star. Therefore, configurations with neutron-star-like compactness can support degenerate resonant islands. This anomaly is reported here for the first time and it is not present in black holes. Such configurations can also support extremely prolonged resonant islands that span from the exterior to the interior of the star and are shielded by thick chaotic layers. We adiabatically evolve inspirals using approximated post-Newtonian fluxes and find time-dependent plateaus in the rotation curves which are associated with island-crossing orbits. Crossings of external islands give rise to typical gravitational-wave glitches found in non-Kerr objects. Furthermore, when an inspiral is traversing an internal island that is surrounded by a thick chaotic layer, a new type of simultaneous multifrequency glitch occurs that may be detectable with space interferometers such as LISA, and can serve as evidence of an extreme-mass-ratio inspiral around a supermassive boson star.

gr-qc↗

arXiv2023

Bayesian parameter estimation on boson-star binary signals with a coherent inspiral template and spin-dependent quadrupolar corrections

Compact boson star binaries are hypothetical sources for ground-based and space gravitational-wave detectors. Their signal would be a messenger for novel fundamental fields and could shed light on the dark matter. In this work, we further develop our analysis in Phys. Rev. D 102, 083002 (2020), aimed at constraining the properties of these objects with future observations. We use a coherent waveform template for the inspiral stage of boson star binaries with large quartic self interactions, including tidal deformability and the nonlinear dependence of the quadrupole moments on the spin in terms of the fundamental couplings of the scalar field theory. Performing a Bayesian analysis, we investigate the ability of a third-generation gravitational-wave detector such as the Einstein Telescope to distinguish these exotic sources from black holes and infer constraints on the fundamental couplings of the model.

gr-qc↗

arXiv2022

The multipolar structure of rotating boson stars

The relativistic multipole moments provide a key ingredient to characterize the gravitational field around compact astrophysical objects. They play a crucial role in the description of the orbital evolution of coalescing binary systems and encode valuable information on the nature of the binary's components, which leaves a measurable imprint in their gravitational-wave emission. We present a new study on the multipolar structure of a class of arbitrarily spinning boson stars with quartic self-interactions in the large coupling limit, where these solutions are expected to be stable. Our results strengthen and extend previous numerical analyses, showing that even for the most compact configurations the multipolar structure deviates significantly from that of a Kerr black hole. We provide accurate data for the multipole moments as functions of the object's mass and spin, which can be directly used to construct inspiral waveform approximants and to perform parameter estimations and searches for boson star binaries.

gr-qc↗

arXiv2021

Gravitational-wave detectors as particle-physics laboratories: Constraining scalar interactions with a coherent inspiral model of boson-star binaries

Gravitational-wave (GW) detections of binary neutron star coalescences play a crucial role to constrain the microscopic interaction of matter at ultrahigh density. Similarly, if boson stars exist in the universe their coalescence can be used to constrain the fundamental coupling constants of a scalar field theory. We develop the first coherent waveform model for the inspiral of boson stars with quartic interactions. The waveform includes coherently spin-induced quadrupolar and tidal-deformability contributions in terms of the masses and spins of the binary and of a single coupling constant of the theory. We show that future instruments such as the Einstein Telescope and the Laser Interferometer Space Antenna can provide strong complementary bounds on bosonic self-interactions, while the constraining power of current detectors is marginal.

gr-qc↗