In any extension of General Relativity (GR), extra fundamental degrees of freedom couple to gravity. Besides deforming GR forecasts in a theory-dependent way, this coupling generically introduces extra modes in the gravitational-wave signal. We propose a novel theory-agnostic test of gravity to search for these nongravitational modes in black hole merger ringdown signals. To leading order in...
The LIGO-VIRGO-KAGRA observations are so far compatible with the Kerr black hole paradigm, though they cannot rule out entirely the existence of black hole mimickers. These are ultra-compact objects that reproduce some observable properties of black holes, while possibly predicting characteristic signatures such as non-trivial tidal deformability and/or repeated gravitational wave echoes in...
Black hole spectroscopy offers insights into the properties of black hole remnants. However, most models assume idealized, vacuum spacetimes, neglecting the astrophysical environments in which black holes reside.
Our most recent results show that the presence of matter halos, such as dark matter distributions, affects the quasinormal modes (QNMs) of black holes. We examined black holes...
The groundbreaking discovery of Gravitational Wave (GW) astronomy in the past decade has significantly advanced our understanding of the gravitational interaction in extreme gravity environments. One of the key scientific goals of future ground-based GW detectors like the Einstein Telescope (ET) is to test Einsteinโs theory of General Relativity (GR) and explore the nature of GW sources, such...
The quasinormal mode spectrum plays a crucial role in modeling post-merger ringdown signals in binary coalescences, encompassing both black holes and ultracompact horizonless objects. However, quasinormal modes areย highly sensitive to small deformations of the system and only describe the linear response within a limited and imprecisely defined timeframe after the merger. Motivated by a...
Binaries of intermediate mass black holes (IMBHs) with masses $M_{\rm bh}=10^2-10^4 M_\odot$ are predicted to emit gravitational waves (GWs) potentially detectable with the Einstein Telescope. Though IMBHs of these masses are widely expected theoretically (and likely hosted in the centre of globular clusters and dwarf galaxies), these objects are very elusive and hard to detect with methods...
Dense stellar clusters provide ideal conditions for the formation of intermediate-mass black holes (IMBHs), i.e. heavy black holes with masses between 100 and 100,000 solar masses. These objects may arise from (i) runaway stellar collisions in light and compact clusters, or (ii) hierarchical binary black hole (BBH) mergers within massive and dense clusters. Assessing the efficiency of both...
The properties of the first stars in the Universe, known as Population III (Pop III) stars, and their remnants are still poorly understood. However, the increased sensitivity of next-generation gravitational wave observatories offers the potential to detect mergers of these early compact binaries at redshifts greater than 15. A fraction of these detections will be loud enough, that is, the...
Population III (Pop. III) stars are ideal candidates for the formation of intermediate-mass black holes (IMBHs, $m = 10^2-10^5\,\rm M_{\odot}$) due to their small mass loss and top-heavy initial mass function. On the other hand, the masses of these IMBHs are typically limited to a few hundred solar masses, restricting their potential as massive black hole seeds. Star cluster dynamics can...
In the last years, gravitational wave detectors proved for the first time the existence of binary black hole mergers. Investigating their formation history can give us an useful insight on poorly constrained binary interaction processes. For instance, the properties of the binary black hole population are heavily influenced by the stability and efficiency of mass transfer events, since...
The stochastic gravitational-wave background (SGWB) generated by the inspiral and merger of binary neutron stars is traditionally modelled assuming that the inspiral is promptly followed by the collapse of the merger remnant to a rotating black hole. While this is reasonable for the most massive binaries, it is not what is expected in general, where a remnant is produced and may survive for up...
Intermediate-mass black holes (IMBHs) are elusive objects that may link stellar mass and supermassive BHs. Scarce observational evidence and theoretical uncertainties make IMBH mysterious objects whose nature represents an open question of modern astrophysics. If IMBHs form, as supported by the theoretical panorama, through interactions and collisions of stars and stellar BHs, they could be...
The rapid formation of supermassive black holes (SMBHs) in the early universe (z > 6) remains one of the most significant mysteries in the Universe. Observations of SMBHs with masses reaching ~ $10^{10} M_{\odot}$ within the first billion years challenge our understanding of black hole (BH) formation and growth. Despite significant insights from the James Webb Space Telescope (JWST), the...
Current gravitational wave (GW) detectors are observing hundreds of binaries in the low-redshift universe, but to fully understand formation mechanisms we must probe the high-redshift regime. Next-generation detectors, such as Cosmic Explorer and Einstein Telescope, will allow us access to redshifts greater than 20, and even upgrades to existing detectors may allow us to probe the...
Quantum chromodynamics predicts a phase transition from hadronic matter to deconfined quarks at extreme densities, yet its exact nature remains uncertain. Neutron stars offer a unique opportunity to probe this transition, but bulk propertiesโmass, radius and tidal deformabilityโprovide only indirect signatures, which require many detections to resolve and are ineffective if the discontinuity...
Although it is conjectured that a phase transition from hadronic to deconfined quark matter is possible in the ultrahigh density environment in Neutron Stars, the nature of such a transition is still unknown. Depending on whether there is a sharp or slow phase transition, one may expect a third family of stable compact stars or โtwin starsโ to appear, with the same mass but different radii...
An understanding of differentially rotating relativistic stars is key to many areas of astrophysics, in particular to the emission of gravitational waves. A newly born, proto-neutron star or a compact
remnant of neutron stars binary merger are expected to rotate differentially and to be important sources of gravitational radiation. A highly accurate and stable, relativistic spectral code is...
Neutron stars having a mass smaller than about 1.17 Ms cannot be produced by any โstandardโ astrophysical mechanism. On the other hand, the analysis of SAX J1808.4-3658 has suggested a mass of about 0.8 Ms, or smaller (Di Salvo et al. MNRAS 483 (2019) 767) and a similar mass has been obtained by the analysis of HESS J1731-347 (Doroshenko et al. Nature Astronomy 2022). Also, masses and...
Euclid is an ESA space mission launched in July 2023, designed to produce an all-sky map of galaxies with unprecedented precision. The mission will survey 14,500 square degrees with its Wide Survey, providing photometric redshifts for galaxies in the range $0
The huge luminosity, the redshift distribution extending at least up to z~10 and the association with the explosive death of very massive stars make long GRBs extremely powerful probes for investigating the early Universe (pop-III stars, cosmic re-ionization, SFR and metallicity evolution up to the โcosmic dawnโ) and measuring cosmological parameters. At the same time, as demonstrated by the...
Next-generation gravitational wave (GW) observatories such as the Einstein Telescope (ET) will observe large numbers of binary neutron star (BNS) mergers across cosmic history and allow us to obtain precise parameter estimates for the events observed at low redshifts. The Vera Rubin Observatory will be a powerful instrument in the discovery and follow-up of optical counterparts of BNS mergers...
I will review the connection between binary neutron star mergers, cosmic rays, and ultra high energy neutrinos. I will discuss the possibility of a multimessenger joint detection of gravitational waves and neutrinos from such mergers.
The Einstein Telescope (ET) will extend the reach of gravitational wave (GW) astronomy for stellar-mass compact binaries to unprecedented distances, significantly enhancing opportunities for multi-messenger discovery. Building on the landmark observations of GW170817 and informed by our recent population modeling studies (Colombo et al. 2022, 2024), we investigate the prospects for detecting...
The Wide-field Spectroscopic Telescope (WST) is an innovative 12-meter-class facility that combines a large field of view (3 square degrees) with a high-multiplex (30,000) multi-object spectrograph operating in both medium- and high-resolution modes (MOS). Additionally, it features a giant panoramic integral field spectrograph (IFS) covering 3ร3 square arcminutes.
WST will produce the...
In this presentation, I will introduce one of our group's ongoing projects, which aims to utilize the post-Newtonian approach implemented in CBwaves for waveform hybridization. In the initial phase, we will assess the compatibility of CBwaves with available numerical waveforms from the SXS collaboration before progressing toward the development of a hybrid model. I will provide an overview of...
We present SEOBNRv5THM, an accurate and fast gravitational-waveform model for quasi-circular, spinning, non-precessing binary neutron stars (BNS) within the effective-one-body (EOB) formalism. It builds on the binary-black-hole approximant SEOBNRv5HM and, compared to its predecessor SEOBNRv4T, it i) incorporates recent high-order post-Newtonian results in the inspiral, including higher-order...
With the observation of the multiple binary inspirals, we begin to question whether the components of the binary areย black holesย or someย exotic compact objectsย (ECOs). Theย "black holeness"ย or the deviation from it can be tested in several ways.ย The distinguishing feature of a black hole from ECOs in the presence of the horizon. This surface acts as a one-way membrane that absorbs energy. Due...
There are a few examples where the accuracy of theoretical predictions is running ahead of that of experiments. One is the case of gravitational waves naturally sourced by hydrodynamical fluctuations in a thermal medium. These signals are motivated by the Standard Model of particle physics, predicting that, for the first three hundred thousand years, the fundamental constituents of the matter...
Wide-band searches for continuous gravitational waves are essential to reveal unknown neutron stars that may be close enough to us to be detectable. Currently, analyses performed on data from 2G detectors for unknown sources cover all possible sky directions, but are restricted in the rotational parameters by their computational cost and by the limited bandwidth of the detectors at low...
The Vera Rubin Observatoryโs (VRO) Legacy Survey of Space and Time (LSST) will revolutionize time-domain optical astronomy, detecting faint sources down to r~27.5 mag and generating nearly 32 trillion observations over 10 years. Among these, ~10 million will be supernovae (SNe), covering a wide range of redshifts and enabling studies of known and rare types, progenitors, and strongly lensed...
I will discuss a recent first-principle derivation of the spectral features of astrophysical stochastic backgrounds produced by populations of compact binary coalescences (CBCs). The treatment is based on the observation that, among the parameters characterizing a CBC, some of them (extrinsic) are distributed uniformly following symmetry principles, while other (intrinsic) carry the more...
The subtraction of the astrophysical foreground to reveal an underlying cosmological stochastic background poses a significant challenge for third-generation detectors. We present a novel approach for characterizing the confusion noise originating from the superposition of undetected astrophysical sources and the residuals from the subtraction of resolved signals, where we average the...
Binary black hole systems are typically assumed to evolve in vacuum. However, the environment surrounding the binary components can influence their properties, such as their tidal deformability, affecting the gravitational waveform produced by the binary and its interpretation in gravitational wave data analysis.
In this talk, focusing on next-generation experiments, such as the Einstein...
Gravitational waves provide a powerful means to perform null tests of strong-gravity physics. Statistical methods based on hierarchical inference, adapted from population studies, have been developed to confidently identify potential signatures of new physics. While these methods are well-suited for detection, they provide limited insight into how exotic physics depends on standard degrees of...
This talk will present the analysis of the first ET MDC using the pygwb pipeline to search for an isotropic stochastic background. We compare the measurement to the theoretical prediction derived from the list of sources and quantify the differences, providing valuable insights into stochastic searches in the presence of high signal-to-noise ratio signals. Additionally, we will discuss the...
Unmodeled data analysis techniques in the LVK collaboration, particularly coherent Wave Burst (cWB), do not assume any physical constraints when detecting GW events. While this allows for the detection of unmodeled signals with great efficiency, it limits the ability to accurately estimate source properties in the case of CBCs. Physics-Informed Neural Networks (PINNs) offer a promising...
With a sensitivity ~10 times that of current-generation gravitational wave (GW) detectors, the Einstein Telescope (ET) should be able to observe thousands of compact binary coalescence (CBC) signals per day, up to a redshift z=20. However, the high rate of signals calls into question whether existing data-analysis methods are directly applicable to ET data. Mock data challenges (MDCs) are...
The Einstein Telescope (ET) and other third-generation (3G) gravitational wave (GW) detectors will be key instruments for detecting gravitational waves (GWs) in the coming decades. However, analyzing the data and estimating source parameters will be challenging, especially given the large number of expected detectionsโbetween $10^4$ and $10^5$ per yearโwhich makes current methods based on...
Third-generation ground-based gravitational wave detectors such as the Einstein Telescope are expected to significantly advance our understanding of compact binary coalescences. One of the most critical challenges in data analysis for the Einstein Telescope is that of overlapping signals. With a tenfold improvement in sensitivity, the Einstein Telescope will be able to detect binary black hole...
Third-generation (3G) gravitational wave (GW) observatories will unveil a cosmic orchestra, detecting thousands of sources annually. However, their increased detection rate poses a major challenge for data analysis. Existing, widely used techniques to obtain the source parameters are prohibitively expensive, creating a bottleneck for extracting scientific insights from 3G detector data. We...
In the planning of a third-generation detector such as the Einstein Telescope, it is crucial to study the impact of technological limitations on the sensitivity, and in turn on the scientific output. In this study, we analyze a set of sensitivity curves corresponding to different technological choices, including worst-case scenarios where each limiting factor is individually considered. We...
