Neutrinos from Supernovae

Neutrinos are fundamental particles in the collapse of massive stars. Because of their weakly interacting nature, neutrinos can travel undisturbed through the stellar core and be direct probes of the still uncertain and fascinating supernova mechanism. Intriguing recent developments on the role of neutrinos during the stellar collapse are reviewed, as well as our current understanding of the flavor conversions in the stellar envelope. The detection perspectives of the next burst and of the diffuse supernova background will be also outlined. High-energy neutrinos in the GeV-PeV range can follow the MeV neutrino emission. Various scenarios concerning the production of high-energy neutrinos are discussed.     

Nucleosynthesis in Supernovae

We present the status and open problems of nucleosynthesis in supernova explosions of both types, responsible for the production of the intermediate mass, Fe-group and heavier elements (with the exception of the main s-process). Constraints from observations can be provided through individual supernovae (SNe) or their remnants (e.g. via spectra and gamma-rays of decaying unstable isotopes) and through surface abundances of stars which witness the composition of the interstellar gas at their formation. With a changing fraction of elements heavier than He in these stars (known as metallicity) the evolution of the nucleosynthesis in galaxies over time can be determined. A complementary way, related to gamma-rays from radioactive decays, is the observation of positrons released in \(\beta^{+}\)-decays, as e.g. from \(^{26}\mbox{Al}\), \(^{44}\mbox{Ti}\), \(^{56,57}\mbox{Ni}\) and possibly further isotopes of their decay chains (in competition with the production of \(e^{+}e^{-}\) pairs in acceleration shocks from SN remnants, pulsars, magnetars or even of particle physics origin). We discuss (a) the role of the core-collapse supernova explosion mechanism for the composition of intermediate mass, Fe-group (and heavier?) ejecta, (b) the transition from neutron stars to black holes as the final result of the collapse of massive stars, and the relation of the latter to supernovae, faint supernovae, and gamma-ray bursts/hypernovae, (c) Type Ia supernovae and their nucleosynthesis (e.g. addressing the \(^{55}\mbox{Mn}\) puzzle), plus (d) further constraints from galactic evolution, \(\gamma\)-ray and positron observations. This is complemented by the role of rare magneto-rotational supernovae (related to magnetars) in comparison with the nucleosynthesis of compact binary mergers, especially with respect to forming the heaviest r-process elements in galactic evolution.     

Cosmic Ray Production in Supernovae

We give a brief review of the origin and acceleration of cosmic rays (CRs), emphasizing the production of CRs at different stages of supernova evolution by the first-order Fermi shock acceleration mechanism. We suggest that supernovae with trans-relativistic outflows, despite being rather rare, may accelerate CRs to energies above \(10^{18}\mbox{ eV}\) over the first year of their evolution. Supernovae in young compact clusters of massive stars, and interaction powered superluminous supernovae, may accelerate CRs well above the PeV regime. We discuss the acceleration of the bulk of the galactic CRs in isolated supernova remnants and re-acceleration of escaped CRs by the multiple shocks present in superbubbles produced by associations of OB stars. The effects of magnetic field amplification by CR driven instabilities, as well as superdiffusive CR transport, are discussed for nonthermal radiation produced by nonlinear shocks of all speeds including trans-relativistic ones.     

Supernovae and the origin of the solar system

This review concentrates on recent ideas involving a relationship between the early solar system and supernova explosions. It summarizes briefly the data that has helped inspire those ideas. Because the true relationship is still unknown and generates controversy, the distinct ideas are introduced singly in the historical context of their origins, and the active sense of surprise and controversy is visible. Quotations from pivotal papers are used as part of the exposition. The subject involves equally the isotopic anomalies detected in meteorites and the dynamic events of galactic evolution, nucleosynthesis, and protosolar collapse. Whatever the correct situation is, new connections have been found between the origin of the elements and the formation of the solar system. The objective of this review is to enable interested space scientists to quickly identify the competing points of view and the experiments and theories that have led to them.     

Models for Type Ia Supernovae and Related Astrophysical Transients

We give an overview of recent efforts to model Type Ia supernovae and related astrophysical transients resulting from thermonuclear explosions in white dwarfs. In particular we point out the challenges resulting from the multi-physics multi-scale nature of the problem and discuss possible numerical approaches to meet them in hydrodynamical explosion simulations and radiative transfer modeling. We give examples of how these methods are applied to several explosion scenarios that have been proposed to explain distinct subsets or, in some cases, the majority of the observed events. In case we comment on some of the successes and shortcoming of these scenarios and highlight important outstanding issues.     

Dust in Supernovae and Supernova Remnants I: Formation Scenarios

Supernovae are considered as prime sources of dust in space. Observations of local supernovae over the past couple of decades have detected the presence of dust in supernova ejecta. The reddening of the high redshift quasars also indicate the presence of large masses of dust in early galaxies. Considering the top heavy IMF in the early galaxies, supernovae are assumed to be the major contributor to these large amounts of dust. However, the composition and morphology of dust grains formed in a supernova ejecta is yet to be understood with clarity. Moreover, the dust masses inferred from observations in mid-infrared and submillimeter wavelength regimes differ by two orders of magnitude or more. Therefore, the mechanism responsible for the synthesis of molecules and dust in such environments plays a crucial role in studying the evolution of cosmic dust in galaxies. This review summarises our current knowledge of dust formation in supernova ejecta and tries to quantify the role of supernovae as dust producers in a galaxy.     

Dust in Supernovae and Supernova Remnants II: Processing and Survival

Observations have recently shown that supernovae are efficient dust factories, as predicted for a long time by theoretical models. The rapid evolution of their stellar progenitors combined with their efficiency in precipitating refractory elements from the gas phase into dust grains make supernovae the major potential suppliers of dust in the early Universe, where more conventional sources like Asymptotic Giant Branch (AGB) stars did not have time to evolve. However, dust yields inferred from observations of young supernovae or derived from models do not reflect the net amount of supernova-condensed dust able to be expelled from the remnants and reach the interstellar medium. The cavity where the dust is formed and initially resides is crossed by the high velocity reverse shock which is generated by the pressure of the circumstellar material shocked by the expanding supernova blast wave. Depending on grain composition and initial size, processing by the reverse shock may lead to substantial dust erosion and even complete destruction. The goal of this review is to present the state of the art about processing and survival of dust inside supernova remnants, in terms of theoretical modelling and comparison to observations.     

The Local Interstellar Medium: Peculiar or Not?

The local Interstellar Medium (ISM) at the 500 pc scale is by many respects a typical place in our Galaxy made of hot and tenuous gas cavities blown by stellar winds and supernovae, that includes the 100 pc wide “Local Hot Bubble (LHB)”, dense and cold clouds forming the cavity “walls”, and finally diffuse and warm clouds embedded within the hot gas, such as the Local Interstellar Cloud (LIC) presently surrounding the Sun. A number of measurements however, including abundance data, have contradicted this “normality” of our interstellar environment. Some contradictions have been explained, some not. I review recent observations at different spatial scales and discuss those peculiarities. At all scales Johannes Geiss has played a major role. At the scale of the first hundred parsecs, there are at least three “anomalies”: (i) the peculiar Gould Belt (GB), (ii) the recently measured peculiar Deuterium abundance pattern, (iii) the low value of the local O, N and ³He gas phase abundances. I discuss here the possibility of a historical link between these three observations: the large scale phenomenon which has generated the Belt, a giant cloud impact or an explosive event could be the common origin. At the 50–100 parsec scale, some of the unexplained or contradictory measurements of the Local Bubble hot gas, including its EUV/soft X ray emissions, ion column-densities and gas pressure may at least partially be elucidated in the light of the newly discovered X-ray emission mechanism following charge transfer between solar wind high ions and solar system neutrals. The Local Bubble hot gas pressure and temperature may be lower than previously inferred. Finally, at the smaller scale of the local diffuse cloudlets (a few parsecs), the knowledge of their structures and physical states has constantly progressed by means of nearby star absorption spectroscopy. On the other hand, thanks to anomalous cosmic rays and pickup ions measurements, local abundances of ISM neutral species are now precisely derived and may be compared with the absorption data. Interestingly these comparisons are now accurate enough to reveal other (noninterstellar) sources of pickup ions. However the actual physical state of the ISM 10–20,000 A.U. ahead along the Sun trajectory, which will be the ambient interstellar medium in a few thousands years, remains unknown. Local Bubble hot gas or warm LIC-type gas? More EUV/UV spectroscopic data are needed to answer this question.     

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目前高职院校在校园文化建设上存在一些问题,致使校园文化不能充分发挥应有作用。要创新高职院校的校园文化,必须体现职业要求、高职特点和办学特色的原则,引入企业文化,加强仿真模拟实践,接轨社会生活。