Physics of Supernovae: theory, observations, unresolved problems
D. K. Nadyozhin
备注：
12 pages, 5 figures. Submitted to the Proceedings of the Baikal Young Scientists' International School (BAYSIS), 17-22 September 2007, Irkutsk, Russia; http://bsfp.iszf.irk.ru/bsfp2007/index.php
The main observational properties and resulting classification of supernovae (SNe) are briefly reviewed. Then we discuss the progress in modeling of two basic types of SNe - the thermonuclear and core-collapse ones, with special emphasis being placed on difficulties relating to a consistent description of thermonuclear flame propagation and the detachment of supernova envelope from the collapsing core (a nascent neutron star). The properties of the neutrino flux expected from the corecollapse SNe, and the lessons of SN1987A, exploded in the Large Magellanic Cloud, are considered as well.
In this paper, we review the present state of theoretical models of thermonuclear supernovae, and compare their predicitions with the constraints derived from observations of Type Ia supernovae. The diversity of explosion mechanisms usually found in one-dimensional simulations is a direct consequence of the impossibility to resolve the flame structure under the assumption of spherical symmetry. Spherically symmetric models have been successful in explaining many of the observational features of Type Ia supernovae, but they rely on two kinds of empirical models: one that describes the behaviour…
The past ten years have seen a tremendous increase in the number of Type Ia supernovae discovered and in the quality of the basic data presented. The cosmological results based on distances to Type Ia events have been spectacular, leading to statistically accurate values of the Hubble constant, Omega_M, and Omega_Lambda. However, in spite of the recent advances, a number of mysteries continue to remain in our understanding of these events. In this short review, I will concentrate on unresolved problems and curious correlations in the data on Type Ia SNe, whose resolution may lead to a deeper u…
Global properties of different types of supernovae are overviewed. A special emphasis is made on the issues of interest both for the supernova and cosmic ray physics such as supernova shock waves and neutrino signal.
Supernovae are nature's grandest explosions and an astrophysical laboratory in which unique conditions exist that are not achievable on Earth. They are also the furnaces in which most of the elements heavier than carbon have been forged. Scientists have argued for decades about the physical mechanism responsible for these explosions. It is clear that the ultimate energy source is gravity, but the relative roles of neutrinos, fluid instabilities, rotation and magnetic fields continue to be debated.
I use photometry and spectroscopy data for 24 Type II plateau supernovae to examine their observed and physical properties. This dataset shows that these objects encompass a wide range in their observed properties (plateau luminosities, tail luminosities, and expansion velocities) and their physical parameters (explosion energies, ejected masses, initial radii, and 56Ni yields). Several regularities emerge within this diversity, which reveal (1) a continuum in the properties of Type II plateau supernovae, (2) a one parameter family (at least to first order), (3) evidence that stellar mass play…
Searching for the presence of circumstellar material is currently the only direct way to discriminate between the different types of possible progenitor systems for Type Ia supernovae. We have therefore looked for narrow H-alpha in a high-resolution spectrum of the normal Type Ia supernova 1994D taken 10 days before maximum and only 6.5 days after explosion. We derive an upper limit of 2.0E-16 erg cm^{-2} s^{-1} for an unresolved emission line at the local H II region velocity. To estimate the limit this puts on wind density, we have made time-dependent photoionization calculations. Assuming s…
This paper summarizes observed and physical properties of all types of core collapse supernovae. Despite the great diversity displayed by these objects, several regularities emerge which suggest that 1) there is a continuum in the properties of these objects, 2) the mass of the envelope is one of the driving parameters of the explosion, or it is correlated with some other property of the core, with the latter determining the outcome of the explosion, and 3) the physics of the core and explosion mechanism of all core collapse supernovae are not be fundamentally different, regardless of the exte…
New simulations demonstrate that low-mode, nonradial hydrodynamic instabilities of the accretion shock help starting hot-bubble convection in supernovae and thus support explosions by the neutrino-heating mechanism. The prevailing conditions depend on the high-density equation of state which governs stellar core collapse, core bounce, and neutron star formation. Tests of this sensitivity to nuclear physics variations are shown for spherically symmetric models. Implications of current explosion models for r-process nucleosynthesis are addressed.
We study the origin of unresolved X-ray emission from the bulge of M31 based on archival Chandra and XMM-Newton observations. We demonstrate that three different components are present: (i) Broad-band emission from a large number of faint sources -- mainly accreting white dwarfs and active binaries, associated with the old stellar population, similar to the Galactic Ridge X-ray emission of the Milky Way. The X-ray to K-band luminosity ratios are compatible with those for the Milky Way and for M32, in the 2 - 10 keV band it is (3.6 +/- 0.2) x 10^27 erg/s/L_sun. (ii) Soft emission from ionized g…
We extend a low Mach number hydrodynamics method developed for terrestrial combustion, to the study of thermonuclear flames in Type Ia supernovae. We discuss the differences between 2-D and 3-D Rayleigh-Taylor unstable flame simulations, and give detailed diagnostics on the turbulence, showing that the kinetic energy power spectrum obeys Bolgiano-Obukhov statistics in 2-D, but Kolmogorov statistics in 3-D. Preliminary results from 3-D reacting bubble calculations are shown, and their implications for ignition are discussed.
We investigate, by numerical simulations, the photometric signature of magnetic flux tubes in the solar photosphere. We show that the observed contrast profiles are determined not only by the physical properties of the tube and its surroundings, but also by the peculiarities of the observations, including the line/continuum formation height and the spatial and spectral resolution. The aim is to understand these contributions well enough so that multi-wavelength observations can begin to disentangle them.
We will briefly discuss the importance of sensitive X-ray observations above 10 keV for a better understanding of the physical mechanisms associated to the Supermassive Black Hole primary emission and to the cosmological evolution of the most obscured Active Galactic Nuclei.
I use photometry and spectroscopy data for 24 Type II plateau supernovae to examine their observed and physical properties. This dataset shows that these objects encompass a wide range of ~5 mag in their plateau luminosities, their expansion velocities vary by x5, and the nickel masses produced in these explosions go from 0.0016 to 0.26 Mo. From a subset of 16 objects I find that the explosion energies vary between 0.6x and 5.5x10^51 ergs, the ejected masses encompass the range 14-56 Mo, and the progenitors' radii go from 80 to 600 Ro. Despite this great diversity several regularities emerge, …
We present observations of 15 massive cores in three different CS transitions from the FCRAO 14m and the KOSMA 3m telescope. We derive physical parameters of these cores using different approaches to the line radiative transfer problem. The local radiative transfer approximations fail to provide reliable values except for the column densities. A self-consistent explanation of the observed line profiles is only possible when taking density gradients and an internal turbulent structure of the cores into account. The observational data can be fitted by a spherically symmetric radiative transfer m…
Thermonuclear supernovae are valuable for cosmology but their physics is not yet fully understood. Modeling the development and propagation of nuclear flame is complicated by numerous instabilities. The predictions of supernova light curves still involve some simplifying assumptions, but one can use the comparison of the computed fluxes with observations to constrain the explosion mechanism. In spite of great progress in recent years, a number of issues remains unsolved both in flame physics and light curve modeling.
The current classification scheme for supernovae is presented. The main observational features of the supernova types are described and the physical implications briefly addressed. Differences between the homogeneous thermonuclear type Ia and similarities among the heterogeneous core collapse type Ib, Ic and II are highlighted. Transforming type IIb, narrow line type IIn, supernovae associated with GRBs and few peculiar objects are also discussed.
We present the results of an ongoing project to use the X-ray observations of Type Ia Supernova Remnants to constrain the physical processes involved in Type Ia Supernova explosions. We use the Tycho Supernova Remnant (SN 1572) as a benchmark case, comparing its observed spectrum with models for the X-ray emission from the shocked ejecta generated from different kinds of Type Ia explosions. Both the integrated spectrum of Tycho and the spatial distribution of the Fe and Si emission in the remnant are well reproduced by delayed detonation models with stratified ejecta. All the other Type Ia exp…
We present a review of X-ray observations of supernovae (SNe). By observing the (~0.1-100 keV) X-ray emission from young SNe, physical key parameters such as the circumstellar matter (CSM) density, mass-loss rate of the progenitor and temperature of the outgoing and reverse shock can be derived as a function of time. Despite intensive search over the last ~25 years, only 15 SNe have been detected in X-rays. We review the individual X-ray observations of these SNe and discuss their implications as to our understanding of the physical processes giving rise to the X-ray emission.
In preparation for a set of hydrodynamical simulations of core-collapse supernovae and protoneutron star winds, we investigate the rates of production and thermalization of $ν_μ$ and $ν_τ$ neutrinos in dense nuclear matter. Included are contributions from electron scattering, electron-positron annihilation, nucleon-nucleon bremsstrahlung, and nucleon scattering. We find that nucleon scattering dominates electron scattering as a thermalization process at neutrino energies greater than $\sim$15 MeV. In addition, nucleon-nucleon bremsstrahlung dominates electron-positron annihilation as a product…
I review the use of type-Ia supernovae (SNe) for cosmological studies. After briefly recalling the main features of type-Ia SNe that lead to their use as cosmological probes, I briefly describe current and planned type-Ia SNe surveys, with special emphasis on their physics reach in the presence of systematic uncertainties, which will be dominant in nearly all cases.
Here I review some nuclear physics aspects of core-collapse supernovae concerning neutrinos. Studies of neutrino emission and interactions in supernovae are crucial to our understanding of the explosion mechanism, the heavy element nucleosynthesis, and pulsar proper motions. I discuss the effects of reduced neutrino opacities in dense nuclear matter on supernova neutrino emission and their implications for the delayed supernova explosion mechanism and the synthesis of neutron-rich heavy elements. I also discuss the effects of parity violation in weak interactions on supernova neutrino emission…
We investigate the photometric signature of magnetic flux tubes in the solar photosphere. We developed two dimensional, static numerical models of isolated and clustered magnetic flux tubes. We investigated the emergent intensity profiles at different lines-of-sight for various spatial resolutions and opacity models. We found that both geometric and photometric properties of bright magnetic features are determined not only by the physical properties of the tube and its surroundings, but also by the particularities of the observations, including the line/continuum formation height, the spatial …
Recent observations have extended the range of diversity among spectra of Type Ia supernovae. I briefly discuss SN Ia explosion models in the spectroscopic context, the observed diversity, and some recent results from direct analysis with the Synow code for one normal and two peculiar SNe Ia. Relating the observational manifestations of diversity to their physical causes is looking like an ever more challenging problem.
We present spectroscopic and photometric data of a sample of Type II plateau Supernovae, covering a wide range of properties, from the $^{56}$Ni rich, high luminosity events (e.g. SN 1992am) to the low-luminosity, $^{56}$Ni poor SNe (e.g. SN 1997D). We provide an observational framework to analyze correlations among observational data, physical parameters and progenitors characteristics of Type II Supernovae.
The gravitational wave signal arising from the collapsing iron core of a Type II supernova progenitor star carries with it the imprint of the progenitor's mass, rotation rate, degree of differential rotation, and the bounce depth. Here, we show how to infer the gravitational radiation waveform of a core collapse event from noisy observations in a network of two or more LIGO-like gravitational wave detectors and, from the recovered signal, constrain these source properties. Using these techniques, predictions from recent core collapse modeling efforts, and the LIGO performance during its S4 sci…
Thanks to a stellar evolution code able to compute through the C-flash we link the binary population synthesis of single degenerate progenitors of type Ia supernovae (SNe Ia) to their physical condition at the time of ignition. We show that there is a large range of possible ignition densities and we detail how their probability distribution depends on the accretion properties. The low density peak of this distribution qualitatively reminds of the clustering of the luminosities of Branch-normal SNe Ia. We tighten the possible range of initial physical conditions for explosion models: they form…
Spectropolarimetry of core collapse supernovae has shown that they are asymmetric and often, but not universally, bi-polar. The Type IIb SN1993J and similar events showed large scatter in the Stokes parameter plane. Observational programs clearly have much more to teach us about the complexity of asymmetric supernovae and the physics involved in the asymmetry. Jet-induced supernova models give a typical jet/torus structure that is reminiscent of some objects like the Crab nebula, SN1987A and perhaps Cas A. Jets, in turn, may arise from the intrinsic rotation and magnetic fields that are expect…
Vastly different time and length scales are a common problem in numerical simulations of astrophysical phenomena. Here, we present an approach to numerical modeling of such objects on the example of Type Ia supernova simulations. The evolution towards the explosion proceeds on much longer time scales than the explosion process itself. The physical length scales relevant in the explosion process cover 11 orders of magnitude and turbulent effects dominate the physical mechanism. Despite these challenges, three-dimensional simulations of Type Ia supernova explosions have recently become possible …
We undertake a theoretical study of the near-infrared (NIR) lightcurves of Type Ia supernovae (SNe Ia). In these bands, the lightcurves are distinguished by a secondary maximum occurring roughly 20 to 30 days after the initial one. Using time-dependent multi-group radiative transfer calculations, we calculate the UBVRIJHK-band lightcurves of model SN Ia ejecta structures. Our synthetic NIR lightcurves show distinct secondary maxima, and provide favorable fits to observed SNe Ia. We offer a detailed explanation of the origin of the NIR secondary maximum, which is shown to relate directly to the…
I summarize, in the form of an extended abstract, the ongoing efforts at the University of Arizona (and in collaboration) to understand core-collapse supernovae theoretically. Included are short discussions of 1D (SESAME) and 2D (VULCAN/2D) codes and results, as well as discussions of the possible role of rotation. Highlighted are recent developments in multi-dimensional radiation hydrodynamics and the essential physics of the neutrino-driven mechanism.
We describe a research program to improve the understanding of Type Ia Supernovae (SNe Ia) by modeling and observing near infrared (NIR) spectra of these events. The NIR between 0.9 microns and 2.5 microns is optimal for examining certain products of the SNe Ia explosion that may be blended or obscured in other spectral regions. NIR analysis will enable us to place important constraints on the physical properties of SNe Ia progenitors and their explosion dynamics. These are critical steps toward understanding the physics of Type Ia Supernovae. We have identified features in NIR spectra of SNe …
Observational advances over the last decade have left little doubt that neutron stars received a large kick velocity (of order a few hundred to a thousand km/s) at birth. The physical origin of the kicks and the related supernova asymmetry is one of the central unsolved mysteries of supernova research. We review the physics of different kick mechanisms, including hydrodynamically driven, neutrino -- magnetic field driven, and electromagnetically driven kicks. The viabilities of the different kick mechanisms are directly related to the other key parameters characterizing nascent neutron stars, …
We investigate the physical conditions where 44Ti and 56Ni are created in core-collapse supernovae. In this preliminary work we use a series of post-processing network calculations with parametrized expansion profiles that are representative of the wide range of temperatures, densities and electron-to-baryon ratios found in 3D supernova simulations. Critical flows that affect the final yields of 44Ti and 56Ni are assessed.
Nearly 4 years ago, two teams of observational astronomers reported that high-redshift Type Ia supernovae are fainter than expected in a decelerating or freely coasting universe. The radical conclusion that the universe has been accelerating in the past few billion years, possibly because of a nonzero value for Einstein's cosmological constant, has gripped the worlds of astronomy and physics, causing a flurry of new research. Having participated on both teams (but much more closely with one than the other), here I provide a personal, historical account of the story.
Core-collapse supernovae are among the most energetic explosions in the universe marking the catastrophic end of massive stars. In spite of rigorous studies for several decades, we still don't understand the explosion mechanism completely. Since they are related to many astrophysical phenomena such as nucleosynthesis, gamma-ray bursts and acceleration of cosmic rays, understanding of their physics has been of wide interest to the astrophysical community. In this article, we review recent progress in the study of core-collapse supernovae focusing on the explosion mechanism, supernova neutrinos,…
We present some results on the study of stellar population properties and distances of galaxies using the SBF technique. The applications summarized here show that the Surface Brightness Fluctuations (SBF) method is able to i) provide accurate distances of resolved and unresolved stellar systems from ~10 Kpc to ~150 Mpc, and ii) to reliably constrain the physical properties (e.g. age and metallicity) of unresolved stellar systems.
It has very recently been demonstrated by Csaki, Kaloper and Terning (CKT) that the faintness of supernovae at high redshift can be accommodated by mixing of a light axion with the photon in the presence of an intergalactic magnetic field, as opposed to the usual explanation of an accelerating universe by a dark energy component. In this paper we analyze further aspects of the CKT mechanism and its generalizations. The CKT mechanism also passes various cosmological constraints from the fluctuations of the CMB and the formation of structure at large scales, without requiring an accelerating pha…
Double-peaked oxygen lines in the nebular spectra of two peculiar Type Ib/c Supernovae (SN Ib/c) have been interpreted as off-axis views of a GRB-jet or unipolar blob ejections. Here we present late-time spectra of 8 SN IIb, Ib and Ic and show that this phenomenon is common and should not be so firmly linked to extraordinary explosion physics. The line profiles are most likely caused by ejecta expanding with a torus- or disk-like geometry. Double-peaked oxygen profiles are not necessarily the indicator of a mis-directed GRB jet.
In this paper we use high quality X-ray observations from XMM-Newton and Chandra to gain new insights into the explosion that originated Tycho's supernova 433 years ago. We perform a detailed comparison between the ejecta emission from the spatially integrated X-ray spectrum of the supernova remnant and current models for Type Ia supernova explosions. We use a grid of synthetic X-ray spectra based on hydrodynamic models of the evolution of the supernova remnant and self-consistent nonequilibrium ionization calculations for the state of the shocked plasma. We find that the fundamental propertie…
Aims: To derive observational properties and physical parameters of the progenitor stars of type IIP supernovae SN 2005ay and SN 2005cs from their U,B,V,R,I CCD photometry, and to define their velocity behaviour. Methods: Light curves are analysed, and the velocities and spectral characteristics of SN 2005cs are obtained using synthetic spectra modeling. Results: Both supernovae are found to be fainter than the average SN IIP, with SN 2005cs being more subluminous and showing slight brightening in the second half of plateau stage in the V,R,I bands and a low expansion velocity. The effects of …
Present and future observations of supernova relic neutrinos (SRNs), i.e., a cosmological neutrino background from past core-collapse supernova explosions, potentially give us useful information concerning various fields of astrophysics, cosmology and particle physics. We review recent progress of theoretical and observational studies of SRNs, particularly focusing on the detectability and also on implications for cosmic star formation history and neutrino physics.
A primary goal for cosmology and particle physics over the coming decade will be to unravel the nature of the dark energy that drives the accelerated expansion of the Universe. In particular, determination of the equation-of-state of dark energy, w equivalent p/rho, and its time variation, dw/dz, will be critical for developing theoretical understanding of the new physics behind this phenomenon. Type Ia supernovae (SNe) and cosmic microwave background (CMB) anisotropy are each sensitive to the dark energy equation-of-state. SNe alone can determine w(z) with some precision, while CMB anisotropy…
