Periodic Reporting for period 1 - JETSET (Launching, propagation and emission of relativistic jets from binary mergers and across mass scales)
Periodo di rendicontazione: 2021-10-01 al 2023-03-31
Relativistic jets are incredible astrophysical phenomena that have fascinated astronomers for decades. They are powerful streams of particles accelerated at nearly the speed of light, associated with events like gamma-ray bursts (GRBs) and active galactic nuclei (AGNs). These jets provide valuable insights into the nature of black holes and the evolution of galaxies. However, they also open many questions. How do rotating black holes generate the immense energy needed to power these jets? How do the jets maintain their stability despite various challenges along their journey? And what causes the emission of light and other forms of energy as the jets travel through space?
JETSET focuses on understanding the formation, propagation, and emission of relativistic jets originating from merging binary systems. It investigates whether similar physical processes are responsible for jet phenomena across a wide range of mass scales, from small black holes to supermassive ones. By studying electromagnetic radiation, neutrinos, and gravitational waves, JETSET is significantly advancing our knowledge of the fundamental nature of spacetime and the intricate dynamics of plasma under extreme conditions, shedding light on the underlying principles that govern our universe.
JETSET focuses on understanding the formation, propagation, and emission of relativistic jets originating from merging binary systems. It investigates whether similar physical processes are responsible for jet phenomena across a wide range of mass scales, from small black holes to supermassive ones. By studying electromagnetic radiation, neutrinos, and gravitational waves, JETSET is significantly advancing our knowledge of the fundamental nature of spacetime and the intricate dynamics of plasma under extreme conditions, shedding light on the underlying principles that govern our universe.
During the initial phase of the project, we focused on exploring the thermodynamics of compact stars as they are behind the potential production of relativistic jets in GRBs (WP1). Using a large number of parameterised equations of state (EOS), we have concluded that neutron stars are likely to have had an interior sound speed above the conformal limit, it (c_s)^2 = 1/3. These results align well with the estimated mass, radius, and tidal deformability obtained from gravitational-wave detectors. More recently, to assess the role played by neutrinos in launching a relativistic jet, we have completed neutrino moment based radiative-transfer code to simulate binary neutron-star mergers. This approach promises to provide reasonably accurate estimates of the energy and momentum losses from the post-merger remnant and and hence determine the physical conditions that could lead to the launching of a relativistic jet.
Further work performed by the JETSET team within WP1 includes a comprehensive study of fully general-relativistic hydrodynamics simulations of binary neutron stars using the V-QCD EOS, which incorporates the possibility of a quark phase appearing during the post-merger phase transition. This scenario could have significant implications for gravitational waves and the merger frequency. Additionally, using fully general-relativistic magnetohydrodynamics (GRMHD) simulations, we have investigated the role of the magnetic field in binary neutron star mergers, particularly in explaining mass ejection, jet launching, and the generation of short gamma-ray bursts. Our research explores the effects of turbulence and Kelvin-Helmholtz instabilities in the crust of neutron stars and the post-merger remnants. These latter study is very important to understand the formation channels of the large magnetic necessary to produce a relativistic jet in a GRB (WP2).
To gain a deeper understanding of particle acceleration within relativistic jets, we employed systematic particle-in-cell (PIC) numerical simulations to investigate the mechanisms behind particle acceleration and plasma heating at microscopic scales (WP1 and WP2). By updating the non-thermal electron and ion distribution functions, our results established a self-consistent connection between electron and proton temperatures, considering macroscopic plasma properties. Overall, our research efforts contribute to advancing the knowledge of jet dynamics in generic jets and shedding light on the processes of jet formation, propagation, and particle acceleration across the mass scale (WP4).
Finally, we analysed the jet dynamics in the M87 galaxy, specifically focusing on the active galactic nuclei, M87*, performing general-relativistic GRMHD simulations to explore the launching and propagation of the jet around a rotating supermassive black hole. We investigated the influence of the accretion disc model and magnetic field morphology, electron temperature, electron distribution function, and black hole rotation (WP1). In addition, we carried out general relativistic radiative transfer (GRRT) calculations to examine the multi-frequency electromagnetic emission. We tested theoretical models and compared them to observations in terms of their morphological features and across their wide electromagnetic spectrum (WP2 and WP5).
Further work performed by the JETSET team within WP1 includes a comprehensive study of fully general-relativistic hydrodynamics simulations of binary neutron stars using the V-QCD EOS, which incorporates the possibility of a quark phase appearing during the post-merger phase transition. This scenario could have significant implications for gravitational waves and the merger frequency. Additionally, using fully general-relativistic magnetohydrodynamics (GRMHD) simulations, we have investigated the role of the magnetic field in binary neutron star mergers, particularly in explaining mass ejection, jet launching, and the generation of short gamma-ray bursts. Our research explores the effects of turbulence and Kelvin-Helmholtz instabilities in the crust of neutron stars and the post-merger remnants. These latter study is very important to understand the formation channels of the large magnetic necessary to produce a relativistic jet in a GRB (WP2).
To gain a deeper understanding of particle acceleration within relativistic jets, we employed systematic particle-in-cell (PIC) numerical simulations to investigate the mechanisms behind particle acceleration and plasma heating at microscopic scales (WP1 and WP2). By updating the non-thermal electron and ion distribution functions, our results established a self-consistent connection between electron and proton temperatures, considering macroscopic plasma properties. Overall, our research efforts contribute to advancing the knowledge of jet dynamics in generic jets and shedding light on the processes of jet formation, propagation, and particle acceleration across the mass scale (WP4).
Finally, we analysed the jet dynamics in the M87 galaxy, specifically focusing on the active galactic nuclei, M87*, performing general-relativistic GRMHD simulations to explore the launching and propagation of the jet around a rotating supermassive black hole. We investigated the influence of the accretion disc model and magnetic field morphology, electron temperature, electron distribution function, and black hole rotation (WP1). In addition, we carried out general relativistic radiative transfer (GRRT) calculations to examine the multi-frequency electromagnetic emission. We tested theoretical models and compared them to observations in terms of their morphological features and across their wide electromagnetic spectrum (WP2 and WP5).
Our team is working on several directions aimed at achieving progress beyond the state-of-the-art. First, we have started long-term fully GRMHD simulations of magnetised binaries aimed at determining the physical conditions that develop over a timescale of a few hundreds of milliseconds in the case in which a black hole is formed and in the case in which a long-lived remant is produced. In this way, it will be possible to contrast the differences in dynamics and assess the role played by the magnetic fields and the presence of a black hole in producing a relativistic jet (WP1). Second, we are developing a robust and highly efficient code to evolve the post-merger remnant up to few seconds. This code uses the conformally flat condition, enabling the evolution of an axisymmetric spacetime in conjunction with the GRMHD equations (WP1). Third, to deepen our understanding of particle acceleration mechanisms in relativistic jets, we are extending our PIC code to incorporate three distinct particle species: ions, electrons, and positrons. This pioneering development will enable the study of particle interactions with electric and magnetic fields, creating a more realistic scenario and assessing the stability properties of relativistic jets (WP2) and the analogies between jets in stellar-mass and supermassive scenarios (WP4). Furthermore, it will be possible to explore the complex dynamics and mechanisms behind particle acceleration in relativistic jets more comprehensively than ever before. Fourth, to explore the dynamics of a jet produced in a binary merger and determine the properties of the breakout, we are assessing the role played by anisotropies and inhomogeneities in the ejected material and their impact one the jet propagation, cocoon formation and afterglow emission (WP3). Finally, exploiting the new data obtained with the observations of the Event Horizon Telescope and leveraging on the theoretical developments mentioned above, we plan to perform a most accurate comparison between the observations and the results of the simulations (WP5).
By the end of the project, the JETSET team aims to significantly enhance our understanding of magnetised jet structures across different scales, including both stellar-mass systems relevant for GRBs and AGNs. In both scenarios, we will employ a vast suite of newly developed numerical tools to investigate jet launching dynamics exploring the effects of the equation of state, a self-consistent treatment of neutrino radiation, spacetime evolution, the extraction of energy from the accretion process and the subsequent dissipation of electromagnetic energy through magnetic reconnection. In this way, we seek to unravel the fundamental mechanisms that govern the formation, propagation, and energy dissipation of these jets.
By the end of the project, the JETSET team aims to significantly enhance our understanding of magnetised jet structures across different scales, including both stellar-mass systems relevant for GRBs and AGNs. In both scenarios, we will employ a vast suite of newly developed numerical tools to investigate jet launching dynamics exploring the effects of the equation of state, a self-consistent treatment of neutrino radiation, spacetime evolution, the extraction of energy from the accretion process and the subsequent dissipation of electromagnetic energy through magnetic reconnection. In this way, we seek to unravel the fundamental mechanisms that govern the formation, propagation, and energy dissipation of these jets.