Over the last two decades astronomy has established the first informative connections between different cosmic messengers, exemplified by the association of electromagnetic emission and the gravitational wave signal produced by the binary neutron star merger GW170817. Milt-messenger astronomy provides crucial insights into the physics of these sources by combining independent messengers....
The fact that a successful jet has been produced in the single well-localised binary neutron star (BNS) merger detected to date in gravitational waves suggests that this is not a rare outcome of this type of mergers. We back this intuitive conclusion with quantitative arguments that constrain the fraction of BNS mergers that produce a successful jet to be larger than about 1/3 at 90%...
Gamma-ray bursts arise from at least two distinct progenitor channels, the collapse of massive stars, and the merger of two compact objects. While both may plausibly yield detectable gravitational wave emission, compact object mergers represent the best prospects for joint electromagnetic and gravitational wave detections in the near-term future. I will review the evidence linking both short-...
On August 17, 2017, the first joint detection of gravitational waves (GWs) and electromagnetic (EM) waves from a binary neutron star (BNS) merger marked the beginning of multi-messenger astronomy with GWs and clearly demonstrated the huge informative power of joint EM and GW observations. In addition to BNS mergers, there is a wide range of highly energetic astrophysical sources expected to...
Millisecond pulsars are ideal targets to probe the strong interaction at supranuclear densities and search for continuous gravitational wave (CW) sources. Either the rotation of their magnetic field or the infall of matter lost by a companion star is assumed to power their electromagnetic emission. Recently, we exploited the fast optical photometer SiFAP2 at 3.6m INAFโs Telescopio Nazionale...
We explore cases of off-equatorial motion of a matter following inclined, almost spherical, relativistically precessing trajectories around a supermassive black hole with the aim of understanding the boundaries between the regions of stable, plunging, and escaping motion. As a generalisation of the Innermost Stable Circular Orbit (ISCO), the concept of the radius of the Innermost Stable...
The study of the thermal and magnetic evolution of neutron stars in time is fundamental to understand the spectral and temporal properties of these sources, shed light on the origin of the different neutron star populations, and constraining the dense matter equation of state. To this aim, a numerical study of the heat diffusion and magnetic evolution equation is required, coupled with a...
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...
Since March 2019, a large international collaboration (known as โTransients and Pulsars with MeerKATโ, or โTRAPUMโ) has been using the 64-antenna MeerKAT radio telescope array in South Africa to search for pulsars in globular clusters. These surveys have been exceptionally successful, with the discovery of almost 100 new pulsars in globular clusters, which represent one third of the current...
TRAnsients and PUlsars with MeerKAT (TRAPUM) is a large survey project using the new MeerKAT radio interferometer to search for pulsars in the southern sky. TRAPUM's targeted searches of globular clusters, nearby galaxies, Galactic nebulae, and gamma-ray sources have led to the discovery of around 150 new pulsars, the majority of which are millisecond pulsars (MSPs) in binary systems. In this...
X-ray pulses of rapidly rotating neutron stars (NSs) can be used to probe both the properties of heated surface regions of a NS and the equation of state (EoS) of high-density matter inside a NS. Constraints on the EoS are obtained by measuring the mass and radius of the NS based on the relativistic effects when photons travel from the stellar surface to the observer. During the last few...
Kilonovae are the optical counterparts to gravitational wave emissions, which are produced by the radioactive decay of heavy elements formed through rapid neutron captures following neutron star mergers. Combining the gravitational wave and kilonova information reveals the characteristics of dense matter, as well as the physical properties of neutron stars such as the equation of state. To...
The availability of accurate astronomical data collected by electromagnetic observatories and gravitational-wave (GW) interferometers, supplemented by the information obtained from Earth-based laboratory experiments, has opened a new era for the investigation of nuclear dynamics in dense matter. Besides being a valuable source of information on average properties, such as the Equation of State...
We present the first application of the BAM code for numerical-relativity simulations of neutron stars (NS) admixed with fermionic dark matter (DM). Employing the Sly4 Equation of State (Sly4) for baryonic matter and treating dark matter as a non-interacting fluid, we investigate the impact of a varying dark matter fraction (0%, 3%, and 15% of the gravitational mass) on the merger dynamics,...
INAF will play a key role in the newborn multi-messenger astronomy field allowing us to study and identify the likely faint and rapidly fading electromagnetic counterparts of the hundreds gravitational wave (GW) events expected by the 2nd generation GW detectors network at full sensitivity together with upcoming electromagnetic facilities like Rubin telescope.
In this talk, I will present all...
Axion dark matter can form stable, self-gravitating objects called axion stars, which are made unstable above a critical mass by their coupling to electromagnetism. In this talk, using numerical relativity, I will demonstrate how two sub-critical axion stars can merge and form a more massive, excited and critical star, which consequently decays through electromagnetic radiation. The whole...
Over 15 years since their discovery, the origin of fast radio bursts (FRBs) still eludes us, despite outstanding progress both observationally and theoretically. The huge FRB luminosities, the apparent dichotomy between one-offs and repeaters, and the lack of bright FRB sources in the local Universe, are just some of the theoretical challenges still facing us. Among the countless theoretical...
Millisecond pulsars are the fastest-spinning compact stars in the Universe. They are prime targets to probe the strong interaction at supranuclear densities and search for continuous gravitational wave sources. A long-standing paradigm assumes that a millisecond pulsar in a binary system, during its evolution, can be powered either by the rotation of the pulsar's magnetic field or by the...
Neutron stars are compact celestial objects that offer the unique opportunity to explore matter and its interactions under conditions that cannot be reproduced elsewhere in the Universe. Their extreme gravitational, rotational and magnetic energy reservoirs fuel their diverse emission properties, which are visible across the electromagnetic waveband as well as the gravitational wave window....
Electromagnetic onstraints on the orbital (and pulsation) parameters of low-mass X-ray binaries are crucial to facilitate sensitive searches for the continuous gravitational waves these systems are theorised to emit.
I will present recent results on behalf of the Precision Ephemerides for Gravitational-wave Searches project on Scorpius X-1 (Killestein et al., 2023), building on previous...
