Les Houches - Lecturers


Aksenov Aleksey      One dimensional simulations of the gravitational collapse of the stellar core and the neutrino luminosity

We compute the collapse of a 1.4M_\odot iron stellar core. The equation of state takes into account photon equilibrium radiation, a mixture of Fermi gases of the free nucleons and ideal gases of Fe, He nuclei in equilibrium relative to nuclear reactions, and an electron-positron gas. The problem includes the Boltzmann kinetic equations for electron neutrino and electron antineutrino. Neutrinos take part in the weak interactions with free nucleons, nuclei, and electrons. In the calculations we took exact expressions for Matrix elements of reactions processes at calculations of reactions rates, like we made in our recent investigations of the pair plasma. We started from near equilibrium polytropes n=3. We evaluated the task till the establishing of the neutron star in the final state. The solution gives neutrino luminosities. The computed luminosities exhibit narrow peaks with character widths of 10 ms with the maximum luminosity 10^54 erg/s due to the shock wave arising at the collapse. Part of the energy of the neutrino radiation is adsorbed by the stellar envelope. But this value \sim10^{50} one order less than the Supernova. Probably to achieve the accordance with the investigations we need take into account 3D consideration.

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Ansoldi, Stefano Emission versus activity of Mrk421

Arnett David Realistic Progenitor Models for Core-Collapse Supernovae

Turbulence in Stars: Significant Progress

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Belvedere Riccardo Mass, Radius and Moment of Inertia of Neutron Stars

Bianco Carlo Luciano The canonical GRB scenario

Within the fireshell model, Gamma-Ray Burst (GRB) light curves are composed by two distinct phenomena: the Proper GRB (P-GRB), emitted when the fireshell becomes transparent, and the extended afterglow, emitted due to the interaction with the CircumBurst Medium (CBM) of the ultrarelativistic baryonic matter shell left over after the transparency point. The peak of the extended afterglow, together with the P-GRB, forms what is usually called the "prompt emission". Such a theoretical framework implies the existence of three GRB classes, as a function of the fireshell baryon loading and of the CBM average density: the "genuine" short GRBs, where the P-GRB is energetically predominant over the extended afterglow, the "long" GRBs, where the extended afterglow is energetically predominant over the P-GRB, and the "disguised" short GRBs, where the extended afterglow, although still energetically predominant, has a peak flux lower than the P-GRB one due to a peculiarly low value of the CBM density, typical of galactic halos. In this talk I will describe the kinematics and dynamics of the fireshell in both the optically thick and the optically thin phase, with special emphasis on the transparency point and on the observational properties of the P-GRB. Such observational properties are crucial for the identification of the P-GRB in the observed GRBs and therefore for their classification in the above recalled three classes.

Bisnovaty-Kogan Gennady Magnetized accretion disks around black holes at high luminosity

The problem of the formation of a large-scale magnetic field in the accretion disks around black holes is reconsidered, with account the nonuniform vertical structure of the disk. The high electrical conductivity of the outer layers of the disk prevents the outward diffusion of the magnetic field. The solution for a stationary state with a large magnetic field in the inner parts of the accretion disk, and strong vertical stratification is analyzed. Global solution of advective accretion disk structure around a black hole is constructed numerically. At high luminosity there is a continuous transition between the optically thick outer and optically thin inner disk regions. Models of accretion flows with large mass accretion rates are considered using a bridging formula for radiative losses at high and low effective optical depths. Contrary to the models neglecting advection, the global solutions have been found for all investigated range of accretion rates. The presence of the effectively optically thin regions in the innermost part of accretion disks results in a significant increase of the plasma temperature in those regions and this increase can be discriminated in observations in the form of the observed hard radiation tails. The temperature of the inner region is increasing with a growth of the angular momentum of the black hole, and may reach pair formation conditions.

Chardonnet Pascal On pair instabilities explosion and gamma ray bursts chardonnet@lapp.in2p3.fr
Chechetkin Valery Mechanisms of Supernova Explosions

In spite of long and intensive research, up to now there is no self-consistent explanation of Supernovae (SN) explosions. According to observations, all Supernovae are divided into two large groups, Type I (SNI) and Type II (SNII), with smaller subgroups. Different physical mechanisms of supernovae are employed to explain SNe of different types. SNI are traditionally explained by thermonuclear explosion of a carbon-oxygen white dwarf, while SNII are related to gravitational collapse of a massive star. Theory of both SNI and II involve a large number of fundamental problems of modern physics and astrophysics, which are not solved yet. The total energy and nucleosynthesis of SNI depends on the dynamics of reaction front in a white dwarf, which may propagate as subsonic deflagration or supersonic detonation. For example, the deflagration model of supernova was suggested in our team in 1974. The most promising models of SNI at present suggest that explosion starts as a deflagration and turns into detonation later. New ideas in development of SNI theory appeared in the last decade, many of them are related to large-scale instabilities of the deflagration front. An initially spherical deflagration front ignited in the star centre becomes unstable with respect to the Rayleigh-Taylor instability, which distorts the front and makes it flow out of the centre in the form of a bubble. Solution to this problem requires 3D numerical simulations of SNI. One of the main problems in the theory of SNII is how a neutron star is born in the explosion. During gravitational collapse of an iron core of a massive star, huge energy is released in the form of neutrino. However, these neutrinos remain trapped in the central layers of the star of super-density. In order to stop the collapse and top support the explosion, the neutrinos have to be transported fast to the bounce shock. Our new results suggest large-scale convection as the main transport mechanism for neutrinos in SNII. High-energy neutrinos are drifted by large bubbles to the outer layers of the star, where they finally escape and reach the bounce shock.
Della Valle Massimo SN Taxonomy

SN-GRB connection
Fuller George Neutrino Flavor Physics in Gravitational Collapse and Cosmology gfuller@ucsd.edu
Izzo Luca   Luca.Izzo@ICRA.it
Lattimer Jim 1. Neutron Star Structure I: General Limits from Theory and the Equation of State Fundamental limits limits to many neutron star properties (mass, radius, rotation rate, central density, magnetic field) are determined by general relativity and causality. Properties of the dense matter equation of state of hadrons and quarks in neutron star matter are reviewed. Nuclear masses, theoretical limits to the properties of pure neutron matter, and laboratory experiments such as heavy ion collisions and neutron skin measurements provide important constraints.

2. Neutron Star Structure II: Recent Observational Constraints The implications of recent pulsar mass and spin measurements, observations of thermal emission from isolated neutron stars, and observations of photospheric radius expansion bursts are discussed. Important limits will also be set by gravitational wave observations of compact star mergers involving neutron stars and moment of inertia measurements from pulsar timing in double neutron star systems.

3. Neutron Star Evolution and Cooling: The birth of neutron stars and neutrino emissions from proto-neutron stars are reviewed. The thermal history of neutron stars, and the possibility of rapid cooling from the direct Urca process, is described and compared to observations of isolated, cooling neutron stars. The recent observations of the neutron star in Cas A which seem to be due to the onset of neutron superfluidity in the star's core is discussed.
Malheiro Manuel SGRs and AXPs: Massive Rotating White Dwarfs versus Magnetars

The recent observations of SGR 0418+5729 offer an authentic Rosetta Stone for deciphering the energy source of Soft Gamma Ray Repeaters (SGRs) and Anomalous X-ray Pulsars (AXPs). It is shown how a consistent model for SGRs and AXPs can be expressed in terms of canonical physics and astrophysics within massive, fast rotating, and highly magnetized white dwarfs.

Meynet George    
Mezzacappa Anthony Lectures in Core Collapse Supernova Theory

Nadyozhin Dmitrij K. The Neutrino Transport in Collapsing Stellar Cores:

I. Neutrino Hydrodynamics

The neutrino transport equation: transparent and opaque cases. General hydrodynamic equations for matter coupled with the neutrino field.

II. The Neutrino Heat Conduction Theory (opaque case)

The derivation of equations for diffusive transport of energy and lepton charge. The case of pure absorption. Incorporation of the neutrino scattering. The Onsager symmetry principle for the kinetic coefficients. Boundary conditions. The characteristic time of the neutrino thermalization.

III. Principal Physical Effects in Collapsing Stellar Cores

The equation of state at NSE: nuclear excited states and coulomb interaction. The short puls of electron neutrinos from nonequilibrium neutronization. Expected expulsion of supernova envelope due to the phase transitions in nuclear matter. The stellar remnants of collapsed-core supernovae: comparison of observational data (Crab, Cas A, SN 1987A, SN 1979C).

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Ott Christian General Relativistic Simulations of Stellar Collapse and Black Hole Formation

Gravitational Waves -- Probes of Compact Object Physics

The Core-Collapse Supernova Mechanism and its Multi-Messenger Signatures

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Patricelli Barbara High energetic Gamma Ray Bursts and their spectral properties within the fireshell model

Pethick Chris Physics of neutron star crusts

The outer part of a neutron star occupies only a small fraction of the total stellar volume but it is important because it is more accessible to observation than is the stellar interior. I shall give a simple introduction to the physics of matter at subnuclear densities and will touch on topics such as the sizes and shapes of atomic nuclei, melting, superfluidity, and collective modes. I shall also describe recent developments on constraining the equation of state of matter at subnuclear densities by many-body theory and the use of effective interactions derived from nucleon-nucleon scattering data.

Popov Mikhail Nucleosynthesis in the pair-instability supernovae with tracer particle method

Inside a core of a $\gtrsim130 M_{\odot}$ star the temperature could reach so high value that electron-positron pairs could be produces. This process reduces the radiation pressure and results in contraction of matter what could trigger the explosive helium burning. Coupled with hydrodynamic processes under the convective instability conditions it will result in pair instability type supernova explosion (PISN). We studied the explosive nucleosynthesis for a $60 M_{\odot}$ helium core of a PISN progenitor star under the development of convective instability. The hydrodynamic simulation was performed in two dimensions on a cylindrical coordinate system assuming rotational symmetry of an exploding star. We used a new low dissipative numerical code based on piecewise parabolic method on local stencil for hydrodynamic simulations. Rotation of a star reinforced the convection bringing matter to the outer regions. Isotopic nucleosynthetic yields was calculated as! a post-processing step by integration of a reaction network over the recorded temperature and density time histories along the paths the tracer particles took in a hydrodynamic simulation. These particles are actually a Lagrangian component set over Eulerian grid. Each tracer represented the same amount of mass a star, but the mass of a tracer did not couple to hydrodynamic flow via gravity or inertia, i.e. tracers passively moved with the flow. The total yield was computed as a sum over all the tracers. The spatial distribution of the species was studied depending on initial conditions.
Rueda Jorge A.   jorge.rueda@ICRA.it
Ruffini Remo   ruffini@icra.it
Titarchuk Lev X-ray spectral index correlations vs mass accretion rate in neutron star and black hole X-ray binaries in their different spectral states. Theory vs observations

I present details of the first principle theory of X-ray spectral formation in neutron star (NS) and black hole (BH) binaries. I show this theory predicts the spectral index correlation vs mass accretion rate as in the case of NS as well in the BH case. In both cases this index correlation is mostly correlated to a ratio of energy release in the disk vs that in transition (boundary) layer . In BHs the spectral index should increase and then saturate with mass accretion rate because the index as an inverse of Comptonization parameter Y and Y-parameter saturates with the high mass accretion in the converging flow onto BH. Comparison of this model prediction with X-ray observations shows that in BH case the index, indeed, correlates and then saturates with mass accretion rate. Moreover this index-mass accretion rate correlation allows us to estimate BH masses and distance to the source. While in NS sources the observations shows that the index! stays the same independently of spectral state of the source which can be possible if the energy release in the disk is always much smaller of that at NS TL (boundary layer).
Vereshchagin Gregory 1. Thermalization of pair plasma with baryonic loading

2. Photospheric emission from relativistic outflows
Xue She-Sheng A study of neutrino productions in gravitational collapses

In order to catch some sight of neutrino production in gravitational collapsing processes, we try to find a simplified model to calculate neutrino production rate based on equilibrium conditions of microscopic processes, provided microscopic process rates are much larger than macroscopic process ones. The preliminary results are consistent with numerical simulations and observational data

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