Matteo Breschi

Matteo Breschi

Gravitational-wave data analysis

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Posts

GGI school on Theoretical aspects of astroparticle physics, cosmology and gravitation

less than 1 minute read

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Astroparticle Physics, Cosmology and Gravitation are nowadays very active areas of research. The School aims at providing robust and detailed introductions on the basic theoretical concepts and tools needed for performing research in these fields. Gravitational waves of astrophysical and cosmological origin, neutrino physics and astronomy, dark matter and dark energy, galactic and extra-galactic cosmic rays and gamma-rays will be some among the main topics. The lecturers are selected among the best experts of our international communities.

Reinterpreting GW190521 as an hyperbolic capture

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One of the most enigmatic and interesting gravitational signals observed by LIGO and Virgo to date, GW190521, may have been generated by the violent collision of two black holes orbiting in an extremely dense and crowded galactic environment just before the merger.

The first ET annual meeting at EGO

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“The ET annual meeting is the 1st event involving the whole ET collaboration after its formal foundation, in June 2022; it is worth to note that in these few months the ET collaboration has grown-up passing the 1300 members – said the ET collaboration spokesperson, Michele Punturo – The ET annual meeting is a pivotal occasion to discuss the recent achievements and to prepare the next steps in the design of the ET observatory, in defining ET science and in setting-up the ET organization.”

Bajes v0.3.0 is available on PyPI

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The latest bajes version (0.3.0) is available on PyPI. You can install the bajes package simply using pipwith the command pip install bajes. Alternatively, you can fork the source code from the GitHub repository.

First observations of mixed binaries

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The Virgo, LIGO and KAGRA scientific collaborations today announced the first observation ever of binary systems consisting of a neutron star and a black hole. This was made possible by the detection, in January 2020, of gravitational signals (nicknamed GW200105 and GW200115 from the dates of their detection) emitted by two systems, in which a black hole and a neutron star, rotating around each other, merged into a single compact object. The existence of these systems was predicted by astronomers several decades ago, but they had never been observed with confidence, either through electromagnetic or gravitational signals, until now.

The most massive black hole collision observed to date

less than 1 minute read

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The LIGO Scientific Collaboration and the Virgo Collaboration announced the discovery of GW190521, the most massive gravitational wave binary observed to date. The two inspiralling black holes had masses of about 85 and 66 solar masses, and resulted in the formation of a black hole remnant of 142 solar masses. This remnant provides the first clear detection of an “intermediate-mass” black hole.

publications

talks

Physik-Combo meeting

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I contributed in the organization of the fall meeting of the Physik-Combo 2020. More information on Indico.

Bajes, Bayesian inference of multimessenger transients

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We present Bajes, a parallel and lightweight framework for Bayesian inference of multimessenger transients based on Markov-chain–Monte-Carlo and nested sampling algorithms. We perform multimessenger inference on the binary neutron star merger GW170817 and its electromagnetic counterpart AT2017gfo. Mapping the ejecta properties resorting to fit formulae calibrated on targeted numerical relativity simulations, it is possible to constrain the measurement of the reduced tidal parameter to Λ = 430±160 at the 90% confidence level. This information can be traslated in terms of the neutron star equation of state, predicting a radius of an irrotational neutron star of 1.4 M⊙ of 11.99±0.84 km. Furthermore, we employ the gravitational-wave pipeline in the study of binary neutron star postmerger injections with a network of five detectors made of LIGO, Virgo, KAGRA and Einstein Telescope. Postmerger signals will be detectable for sources at <80 Mpc, with Einstein Telescope contributing over 90% of the total signal-to-noise ratio.

Constraints on nuclear equations of state from binary neutron star mergers

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Multi-messenger observations of binary neutron star mergers can provide essential information on the properties of the nuclear equation of state of these compact objects. We perform Bayesian inference on GW170817 and its kilonova counterpart AT2017gfo, constraining the radius of a neutron star of 1.4 M⊙ to 12.2±0.5 km (1σ level). Furthermore, we show how post-merger gravitational-waves can inform us on the high-density regimes: such observation would constrain the maximum central density of a non-rotating neutron star with an error of the order of ~15% at the 90% confidence level.

Multi-messenger Bayesian analysis of binary neutron start mergers

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The joint detection of the GW170817 and its electromagnetic counterparts is a milestone in multi-messenger astronomy and it can provide constraints on the neutron star equation of state. The LIGO-Virgo data of GW170817 are analyzed using different template models focusing on the implications for neutron star matter properties. We study AT2017gfo using semi-analytical model showing that observational data favor multi-component anisotropic geometries to spherically symmetric profiles. By joining the GW170817 and AT2017gfo information with the NICER measurements, we constrain the radius of a neutron star of 1.4 M⊙ to 12.4±0.7 km (90% confidence level). Finally, we explore future extreme-matter constraints delivered by postmerger gravitational-waves from binary neutron star remnants with next-generation detectors. Postmerger remnants can probe the high-density regimes of the nuclear equation of state, allowing the inference of the maximum neutron star mass with an accuracy of 12% (90% confidence level). Moreover, these transients can be used to infer the presence of non-nucleonic matter phases through the inference of softening of the equation of state.

teaching

Gravitational-wave class 2019-2022

M.Sc. course, Theoretisch-Physikalisches Institut, Friedrich-Schiller-Universität Jena, 2019

I contributed as tutor for the gravitational-wave class of Prof. Bernuzzi during the summer semesters 2019, 2020, 2021 and 2022. The summary page of the class can be found at Bernuzzi’s teaching page. The arguments of the class were:

  • Linearization around flat spacetime
  • Energy, propagation, and interaction
  • Generation of gravitational waves in linearized theory
  • Gravitational-wave sources
  • The post-Newtonian expansion
  • Linearization around black holes
  • Effective-one-body description of the general-relativistic 2-body problem
  • Strong, self-gravity and high-velocities source
  • Gravitational-wave experiments and data analysis