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Register a new userMulti-messenger Astronomy: a Bayesian approach
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Added by
Guillermo Torralba Elipe
Publication date
2017
fields
Physics
and research's language is
English
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After the discovery of the gravitational waves and the observation of neutrinos of cosmic origin, we have entered a new and exciting era where cosmic rays, neutrinos, photons and gravitational waves will be used simultaneously to study the highest energy phenomena in the Universe. Here we present a fully Bayesian approach to the challenge of combining and comparing the wealth of measurements from existing and upcoming experimental facilities. We discuss the procedure from a theoretical point of view and using simulations, we also demonstrate the feasibility of the method by incorporating the use of information provided by different theoretical models and different experimental measurements.
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At the time of defining the science objectives of the INTernational Gamma-Ray Astrophysics Laboratory (INTEGRAL), such a rapid and spectacular development of multi-messenger astronomy could not have been predicted, with new impulsive phenomena becoming accessible through different channels. Neutrino telescopes have routinely detected energetic neutrino events coming from unknown cosmic sources since 2013. Gravitational wave detectors opened a novel window on the sky in 2015 with the detection of the merging of two black holes and in 2017 with the merging of two neutron stars, followed by signals in the full electromagnetic range. Finally, since 2007, radio telescopes detected extremely intense and short burst of radio waves, known as Fast Radio Bursts (FRBs) whose origin is for most cases extragalactic, but enigmatic. The exceptionally robust and versatile design of the INTEGRAL mission has allowed researchers to exploit data collected not only with the pointed instruments, but also with the active cosmic-ray shields of the main instruments to detect impulses of gamma-rays in coincidence with unpredictable phenomena. The full-sky coverage, mostly unocculted by the Earth, the large effective area, the stable background, and the high duty cycle (85%) put INTEGRAL in a privileged position to give a major contribution to multi-messenger astronomy. In this review, we describe how INTEGRAL has provided upper limits on the gamma-ray emission from black-hole binary mergers, detected a short gamma-ray burst in coincidence with a binary neutron star merger, contributed to define the spectral energy distribution of a blazar associated with a neutrino event, set upper limits on impulsive and steady gamma-ray emission from cosmological FRBs, and detected a magnetar flare associated with fast radio bursting emission.
Common analysis techniques in multi-messenger astronomy involve hypothesis tests with unbinned log-likelihood (LLH) functions using data recorded in celestial coordinates to identify sources of high-energy cosmic particles in the Universe. We present the new Python-based tool SkyLLH to develop such analyses in a telescope-independent framework. The main goal of the software is to provide an easy-to-use and modularized concept to implement and to execute such LLH functions efficiently on the computer with high-performance. SkyLLH can be applied on different multi-messenger data like neutrino and gamma-ray events from experiments such as the IceCube Neutrino Observatory and the Fermi-LAT. In this contribution we highlight SkyLLHs various design goals, current development status, and prospects for its wider application in multi-messenger astronomy.
The field of time-domain astrophysics has entered the era of Multi-messenger Astronomy (MMA). One key science goal for the next decade (and beyond) will be to characterize gravitational wave (GW) and neutrino sources using the next generation of Extremely Large Telescopes (ELTs). These studies will have a broad impact across astrophysics, informing our knowledge of the production and enrichment history of the heaviest chemical elements, constrain the dense matter equation of state, provide independent constraints on cosmology, increase our understanding of particle acceleration in shocks and jets, and study the lives of black holes in the universe. Future GW detectors will greatly improve their sensitivity during the coming decade, as will near-infrared telescopes capable of independently finding kilonovae from neutron star mergers. However, the electromagnetic counterparts to high-frequency (LIGO/Virgo band) GW sources will be distant and faint and thus demand ELT capabilities for characterization. ELTs will be important and necessary contributors to an advanced and complete multi-messenger network.
We present a first step in developing a benchmark equation-of-state (EoS) model for multi-messenger astronomy that unifies the thermodynamics of quark and hadronic degrees of freedom. A Lagrangian approach to the thermodynamic potential of quark-meson-nucleon (QMN) matter was used. In this approach, dynamical chiral-symmetry breaking is described by the scalar mean-field dynamics coupled to quarks and nucleons and their chiral partners, whereby its restoration occurs in the hadronic phase by parity doubling, as well as in the quark phase. Quark confinement was achieved by an auxiliary scalar field that parametrizes a dynamical infrared cutoff in the quark sector, serving as an ultraviolet cutoff for the nucleonic phase space. The gap equations were solved for the isospin-symmetric case, as well as for neutron star (NS) conditions. We also calculated the mass-radius (MR) relation of NSs and their tidal deformability parameter. The obtained EoS is in accordance with nuclear matter properties at saturation density and with the flow constraint from heavy ion collision experiments. For isospin-asymmetric matter, a sequential occurrence of light quark flavors is obtained, allowing for a mixed phase of chirally-symmetric nucleonic matter with deconfined down quarks. The MR relations and TDs for compact stars fulfill the constraints from the latest astrophysical observations for PSR J0740+6620, PSR J0030+0451, and the NS merger GW170817, whereby the tension between the maximum mass and compactness constraints rather uniquely fixes the model parameters. The model predicts the existence of stars with a core of chirally restored but purely hadronic (confined) matter for masses beyond $1.8~M_odot$. Stars with pure-quark matter cores are found to be unstable against the gravitational collapse. This instability is shifted to even higher densities if repulsive interactions between quarks are included.
The ANTARES Collaboration has completed in 2008 the deployment of what is currently the largest high energy neutrino detector in the Northern hemisphere. The search for cosmic neutrinos in the energy range between tens of GeV and tens of PeV is performed by means of a three dimensional array of photomultiplier tubes (PMTs), arranged on 12 vertical structures (strings) located in the Mediterranean Sea at a depth of about 2500 meters. The detection principle relies on the identification of the Cherenkov light produced as ultra-relativistic muons propagate in water. The main goal of the detector is the search for point-like sources of cosmic neutrinos from both Galactic and extra-Galactic sources. Besides the search for point sources, other analysis topics are strongly pursued and will be described in the following.
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