1 - INAF-Osservatorio Astronomico di Palermo, Italy
2 - Università degli Studi di Palermo, Italy
3 - Institute for Applied Problems in Mechanics and Mathematics, Lviv, Ukraine
4 – INAF-Osservatorio Astronomico di Padova, Italy
5 – INAF-Osservatorio Astronomico di Roma, Italy
6 - Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo, Japan
7 - INFN. Sezione di Perugia, Italy
8 – INAF-Istituto di Astrofisica e Planetologia Spaziali, Rome, Italy
9 - Monash Centre for Astrophysics (MoCA), Monash University, Victoria, Australia
GalRSG: A long-term monitoring campaign of Galactic Red Supergiants and the quest for SN explosions’ premonitory signs
GalRSG is a new long-term INAF-TNG-REM and a INAF-VST approved monitoring program of a few hundreds selected low-mass Galactic Red Super Giants (RSG) which also makes use of a 36cm telescope at INAF-OAPa. The project is aimed at the detection of transients and variability which could be related to the very late evolutionary stage of these stars, with particular reference to pre-supernova outbursts possibly related to imminent SN explosion. The multi-wavelength coverage (which include both optical and Near Infrared bands) and the short cadence (≤ few days) are fundamental requirements. We will introduce the GalRSG project outlining its legacy value and presenting some preliminary results.
Probing the life and death of massive stars: unveiling the CSM structure and progenitor mass-loss history of SN 2014C
The remnants of core-collapse supernovae (SNe) encode valuable information about the SN engine and the structure of the inhomogeneous ambient medium through which they expand. Analyzing observations of these remnants can yield crucial insights into the SN event itself and the progenitor stellar system. Particularly intriguing are SNe where the expelled material interacts significantly with their surroundings during the early phases of evolution. Such interactions can provide valuable insights into mass-loss events that occurred centuries to millennia before the SN explosion, thus allowing to shed light on the terminal stages of massive star evolution and the elusive mechanisms driving their mass loss.
Here, we present 3D hydrodynamical modeling aimed at describing the evolution of SN 2014C, a well-studied interacting SN observed in the X-ray band with Chandra and NuSTAR. The model describes the evolution of the progenitor star, the SN, and the SN remnant interacting with a dense and inhomogeneous circumstellar medium (CSM). By comparing the model results with X-ray observations, we are able to constrain the structure and geometry of the CSM and the mass-loss history of the progenitor stellar system. Moreover, we are able to disentangle the respective contributions to multi-epoch X-ray spectra from the shocked CSM and the shocked ejecta. We propose that by comparing the constrained mass-loss history from our model with different scenarios involving violent mass-loss before the collapse of the progenitor star, it may be possible to identify the progenitor stellar system of SN 2014C.
Low-energy cosmic rays: effects on chemistry of molecular clouds
Low-energy (<1 TeV) cosmic rays are a key element in several physical and chemical processes of the interstellar medium, from the large scales of molecular clouds to the small scales of protostellar systems. During the last decade, significant progress has been made in understanding their transport regimes at different depths of a cloud and their interaction with magnetic fields. I will focus on the role of cosmic rays in the origin of interstellar chemistry showing how observations of molecular species can yield insights into the interstellar and local cosmic-ray spectrum.
Are FRBs linked with SNRs/PULSARs/PWNae?
Fast Radio Bursts are currently a major subject of research in the astrophysics community, regularly deserving new unexpected discoveries. I will first focus on the possibility that these events are somehow linked with the main cosmic objects explored during Rino’s career, i.e. SNRs and/or Pulsars and/or PWNae. Then I will present a new experiment, which INAF is involved in, and which promises to play a major role in this field for the remainder of this decade.
The escape of cosmic rays from sources
The escape of accelerated particles from their sources is a complex and poorly understood phenomenon. Recent theoretical advances and new observations of high energy radiation from the regions around sources are shedding some light on this phenomenon. I will discuss some of these aspects with emphasis on self-confinement, namely the generation of plasma perturbations induced by cosmic ray currents, with applications to supernova remnants and pulsar wind nebulae.
CubeSats and Distributed Astronomy: from the HERMES fleet to the flight of the ALBATROS, surfing the waves of quantum space-time
ALBATROS (Astonishingly Long Baseline Array Transients Reconnaissance Observatory in Space) is an ambitious astrophysical mission concept that uses a fleet of three small satellites to create an high-energy all-sky monitor with excellent localisation capabilities. The proposed orbits for the spacecrafts are three independent Earth-trailing heliocentric orbits, that will form a nearly equilateral triangular formation with 2.5 106 km arm length: the so-called cart-wheel formation. Each satellite is equipped with two opposite facing ∼ 500 cm2 effective area detectors each consisting of a segmented array of crystal scintillators (GAGG) with a half-sky Field of View, keV-MeV energy band, and temporal resolution better than one microsecond. Thanks to the million km baselines, temporal triangulation techniques allow unprecedented location accuracies, few arc-second/few arc-minutes, for bright/faint transients in a wide energy band, few keV-few MeV crucial for hunting the elusive electromagnetic counterparts of Gravitational Waves, that will play a paramount role in the future of Multi-messenger Astronomy.
This project is an example of high-energy distributed astronomy: a new concept of modular observatory consisting of a fleet of small satellites displaced over a large array, with sub-microsecond time resolution and wide energy band (keV-MeV). A pathfinder of ALBATROS is already under development through the HERMES (High Energy Rapid Modular Ensemble of Satellites) and SpIRIT (Space Industry Responsive Intelligent Thermal Nanosatellite) projects: a fleet of six 3U cube-sats (HERMES) to be launched by the end of 2023 plus one 12U cube-sat (SpIRIT) to be launched by the end of 2022. ALBATROS will furnish the golden sample of GRBs needed to test the dispersion law theorised by some Quantum Gravity theories, which predict relative discrepancies of the speed of photons w.r.t. the speed of light proportional to the ratio of the photon energy to the Planck energy. This effect is extremely small, and GRBs occurring at cosmological distances represent the ideal target to explore it. We describe a compelling approach to this problem that statistically combines a large number of GRBs for which light-curves of the prompt emission over a wide energy band (keV-MeV) are available, and distances are known. We discuss how a golden sample of ∼ 1000 GRBs with known redshift is sufficient to effectively constrain this dispersion law.
CubeSats and Distributed Astronomy: from the HERMES fleet to the flight of the ALBATROS, surfing the waves of quantum space-time
Pulsars are extremely stable natural clocks and, when found in relativistic binary systems, they can be used as exceptional laboratories to test Relativistic gravity in the strong field regime. In this talk I will present the results obtained in this context by studying the now 20-year-long dataset on the double pulsar system J0737-3039A/B, the only binary hosting two active radio pulsars, and one of the most relativistic systems known to date. The double pulsar laboratory has indeed allowed us to confirm the validity of GR at least at 99.99% and to measure several relativistic effects for the firts time.
1 - Università degli Studi di Firenze, Italy
2 - INFN Sezione di Firenze, Italy
3 - INAF-Osservatorio Astrofisico di Arcetri, Italy
Relativistic MHD turbulence simulations and synchrotron polarization properties of Pulsar Wind Nebulae
Pulsar Wind Nebulae, and the Crab Nebula in particular, are among the best laboratories for high-energy astrophysics, where ultra-relativistic electrons are accelerated, emitting synchrotron and Inverse Compton. The IXPE satellite has recently produced X-ray polarimetry maps in the keV range, suggesting a patchy distribution of turbulence with varying properties throughout the nebula. 3D numerical simulations of relativistic turbulence in a magnetically dominated plasma are performed, with a novel GPU-accelerated version of the ECHO code for special and general relativistic MHD, and synthetic synchrotron polarization maps are produced for several levels of magnetization and fluctuations amplitude. Results are discussed and compared to analytical recipes for the averaged polarization degree in the presence of Gaussian magnetic fluctuations.
Bow shock nebulae and their parent pulsars in far-UV
We all know about H-alpha (more generally, Balmer-line) bow shock nebulae (BSNe) created by pulsars moving supersonically in the ISM. The Balmer line emission is generated in the process of de-excitation of most abundant ISM Hydrogen atoms excited when they pass through the shock front. Observing various pulsars in far-UV (1250-2000 A) with the Hubble Space Telescope, we serendipitously discovered far-UV BSNe that had not been predicted by theoretical models and whose nature is unclear yet. I will describe the observed properties of these spectacular objects, including the recently discovered far-UV BSN around the middle-aged pulsar J1741-2054. In addition, I will overview the far-UV observations of their parent pulsars and briefly discuss most important inferences from the observational results.
Probing Magnetic Fields in Young Supernova Remnants with IXPE
Particle acceleration by fast shocks in supernova remnants (SNRs) is believed to produce a significant fraction of Galactic cosmic rays up to energies of hundreds of TeV. Direct signatures of the electron component of this relativistic particle population is observed in the form of X-ray synchrotron radiation. The acceleration process itself is understood to amplified magnetic fields, and the geometry and levels of turbulence in those fields strongly impact the efficiency of the acceleration along with the maximum particle energy. The magnetic field structure, in turn, can be modified considerably by both the ambient medium and the accelerated particles themselves.
Synchrotron emission from the shock regions - through its polarization - provides crucial details about the magnetic field strength and orientation. Due to the rapid losses of the highest-energy particles, X-ray polarization measurements provide probes of the magnetic field very close to the sites of particle acceleration. Measurements of both the geometry of the field and the levels of turbulence implied by the observed polarization degree thus provide unique insights into the conditions leading to particle acceleration in fast shocks. The Imaging X-ray Polarimetry Explorer (IXPE) has carried out observations of multiple young SNRs, including Cas A, Tycho, SN 1006, and RX 1713.7-3946. In each, significant X-ray polarization detections provide measurements of magnetic field properties that show some common behavior but also considerable differences between these SNRs. Here I provide a summary of results from IXPE studies of young SNRs, providing comparisons between the observed polarization and the physical properties of the remnants and their environments.
Rhinos in the room: Sacrificing the important for the urgent when modelling pulsar wind nebulae
I will bring forward some provocative thoughts regarding the modelling of pulsar wind nebulae (PWN), especially at the radiative level, which I think deserve some notes of caution and care. I will mention about caveats in adopting approximations related to the diffusion-loss equation for PWN particles, the treatment of convection, the use of hadronic emission compared with the quality of data, fitting parameters degeneracy and local minima, and issues regarding assumptions usually taken for the location of the shock positions and the treatment of reverberation.
Balmer-dominated shocks in the remnants of Tycho and SNR 0509-67.5
The optical emission from the forward shock of supernova remnants (SNRs) passing through a partially ionized medium exhibits distinct Balmer-line profiles comprising multiple components. Arising from different populations and mechanisms, thorough analysis of these profiles can lead to a deeper comprehension of the environmental conditions, the structure of the shock, and the particle acceleration at the shock, thereby offering valuable insights into the evolutionary dynamics and energetic processes within SNRs. I will discuss the necessity of high spatial and spectral resolution data, as well as the Bayesian inference for data analysis, to accurately interpret the findings. Some data and results will be presented for the Galactic SNR Tycho and the SNR 0509-67.5 in the Large Magellanic Cloud.