Periodic Reporting for period 3 - SNeX (The origins of thermonuclear supernova explosions)
Periodo di rendicontazione: 2023-08-01 al 2025-01-31
Supernovae (SNe) are some of the most energetic explosions in the universe. They play an important role in the evolution of galaxies and the build-up of the chemical composition of the universe and stars. SNe are divided between type Ia, and type II/Ib/Ic SNe. Type Ia SNe are thought to arise from the thermonuclear explosions of white dwarfs (WDs), either following long-term accretion of material from a stellar companion on a WD, which eventually leads to a detonation and the explosion of the WD; or through the merger of two WDs which triggers an explosion. Most type Ia SNe have similar/standardizable properties, allowing their use as "standard candles" and their use in accurate measurement of cosmic distances. These were used to discover the accelerated expansion of the universe and the possible existence of dark energy. Given their major role in astronomy, such SNe have been extensively studied, but nevertheless, their exact origins are still debated. Moreover, over the last two decades, and in particular the advent of large SN surveys have revealed the existence of a wide variety of non-standard sub-types/families of peculiar SNe. Such SNe shows different properties than the regular I SNe, but their estimated rates appear to be comparable to those of standard Ia's, yet they have generally attracted much less attention, given that their peculiarities prohibit their use as good cosmic distance measurement tools. Such SNe, however, still play an important role in the chemical evolution of the universe as they may produce different elemental compositions than the standard Ia's. In addition, the various properties of such SNe open a wide range of questions regarding their origins, which are very likely to provide clues and novel solutions to the origins of standard type Ia SNe and link together the various types of observed SNe. In the ERC project, we explore all types of thermonuclear explosions of white dwarfs producing both "normal" and peculiar SNe and develop novel explosion models to explain their origin, characterize their properties and directly relate them to observations. We use extensive simulations, in order to explore a large phase space of initial conditions and formation channels. The results are then followed using radiative transfer code allowing us to provide detailed predictions for the observable properties arising from each of our theoretical models (light-curve, spectra) and derive the chemical composition of the SN ejecta. A wide range of scenarios are explored; in particular realistic initial conditions derived from full binary stellar evolution; the study of the merger of strange hybrid WDs not yet explored before; and exploring detailed studies of violent mergers and the role played by Helium in such mergers; in addition, we characterize the observable properties of Neutron star-white dwarf mergers that may also give rise to peculiar SNe. In addition, we explore the expected rates and type of galaxies where such SNe are likely to explode and use the models and the observational constraints to link the theoretical models to the observed families of peculiar SNe.
Understanding the origin of such SNe is a crucial part of our understanding of the evolution of the universe, the origin of the elements, and essentially trying to answer key issues about the universe at large, questions raised by humanity already thousands of years ago, and accompanying us to this day.
Understanding the origin of such SNe is a crucial part of our understanding of the evolution of the universe, the origin of the elements, and essentially trying to answer key issues about the universe at large, questions raised by humanity already thousands of years ago, and accompanying us to this day.
During the reporting period, we have made significant progress. We have made 3D models of WD mergers, showing that early small ~10^-3 Msun Helium accretion on a <=1 Msun Carbon-Oxygen WD during a merger does not lead to its explosion and the production of type Ia supernova as suggested by others. We have made models for the disruptions of WDs by neutron stars and stellar black holes and showed they produce peculiar faint and fast red transients, potentially observable by the next generation of transient surveys (Rubin telescope). We were able to provide the first consistent model (using 2D simulations) for the origin of Ca-rich SNe, from the merger of low-mass hybris WD and a low-mass hybrid Carbon-Oxygen-Helium WD, which reproduces the light curve and spectra of such peculiar SNe; we also studied the distribution of Ca-rich SNe in galaxies, showing such SNe are consistent with arising from relatively old environments, and showed that such old progenitor population can explain the existence of such SNe at the outskirts of galaxies dominated by old stellar populations.
In addition, we studied various aspects of the evolution of binary and triple systems which can also give rise to WD mergers and mass transfer. As part of that, we have studied the phase of common envelope evolution of evolved binaries, which plays a critical part in the formation of compact WD binaries that could later merge, as well as studied the dynamic of chaotic three-body encounters which play a key role in the formation of compact binaries in dense stellar systems such as globular clusters. We have also explored the interaction of stars and binaries with gas and the role of gas-embedded stars and binaries in producing compact binaries and mergers. We have also studied the observational properties of SNe exploding in such gas-rich environments, giving rise to distinct features quite different from those of SNe exploding in gas-poor environments. Finally, we have also begun to explore the role of thermonuclear explosions in core-collapse SNe.
These studies have been published in 17 refereed papers and were presented in numerous conferences, seminars, colloquia, popular science talks, press releases, and radio interviews.
In addition, we studied various aspects of the evolution of binary and triple systems which can also give rise to WD mergers and mass transfer. As part of that, we have studied the phase of common envelope evolution of evolved binaries, which plays a critical part in the formation of compact WD binaries that could later merge, as well as studied the dynamic of chaotic three-body encounters which play a key role in the formation of compact binaries in dense stellar systems such as globular clusters. We have also explored the interaction of stars and binaries with gas and the role of gas-embedded stars and binaries in producing compact binaries and mergers. We have also studied the observational properties of SNe exploding in such gas-rich environments, giving rise to distinct features quite different from those of SNe exploding in gas-poor environments. Finally, we have also begun to explore the role of thermonuclear explosions in core-collapse SNe.
These studies have been published in 17 refereed papers and were presented in numerous conferences, seminars, colloquia, popular science talks, press releases, and radio interviews.
Until the end of the reporting period we expect to provide 2D and 3D models of a wide range of WD mergers, and their expected observational properties, and compare them with observations. We hope to be able to provide a consistent model both for normal type Ia SNe, which we believe can be produced mainly through tidal disruptions of hybrid WDs by CO WD, and doe peculiar types of SNe, such a 2008ha-like SNe, Ca-rich SNe, and 2002es SNe. As discussed above we have already provided 2D models for Ca-rich SNe and normal type Ia SNe, but such models have various caveats, and we provide never-before-explored 3D models of such SNe. In addition, we suggest that type 2002cx-like SNe (type Iax SNe) can be produced from a partial deflagration explosion of near-Chandrasekhar WDs, and we will explore the conditions leading to such SNe. We also plan to run 3D models of other types of WD merges and collisions both with other types of WDs as well as neutron stars and black holes. These could direct future observations of faint transients and could play a key role in the interpretation of data from the Rubin telescope. In addition, we will continue to study the processes involved in binary evolution leading to WD mergers and explosions and use population synthesis studied to characterize the rates, delay-time distributions, and host galaxy distributions of the various SNE types we explore.
If fully successful, our research will provide a comprehensive explanation for the origins of type Ia SNe, one of the most important unsolved questions in modern astronomy, which has major ramifications for our understanding of the origins of the elements, and evolution of stars and galaxies, and for the use SNe in measuring the fundamental properties of the universe.
If fully successful, our research will provide a comprehensive explanation for the origins of type Ia SNe, one of the most important unsolved questions in modern astronomy, which has major ramifications for our understanding of the origins of the elements, and evolution of stars and galaxies, and for the use SNe in measuring the fundamental properties of the universe.