Part I. Astronomical Background: 1. High energy astrophysics - an introduction 2. The stars and stellar evolution 3. The galaxies 4. Clusters of galaxies Part II. Physical Processes: 5. Ionisation losses 6. Radiation of accelerated charged particles and bremsstrahlung of electrons 7. The dynamics of charged particles in magnetic fields 8. Synchrotron radiation 9. Interactions of high energy photons 10. Nuclear interactions 11. Aspects of plasma physics and magnetohydrodynamics Part III. High Energy Astrophysics in our Galaxy: 12. Interstellar gas and magnetic fields 13. Dead stars 14. Accretion power in astrophysics 15. Cosmic rays 16. The origin of cosmic rays in our galaxy 17. The acceleration of high energy particles Part IV. Extragalactic High Energy Astrophysics: 18. Active galaxies 19. Black holes in the nuclei of galaxies 20. The vicinity of the black hole 21. Extragalactic radio sources 22. Compact extragalactic sources and superluminal motions 23. Cosmological aspects of high energy astrophysics Appendix References Index.

High Energy Astrophysics

The disruption of stars by supermassive black holes has been linked to more than a dozen flares in the cores of galaxies out to redshift z ~ 0.4. Modeling these flares properly requires a prediction of the rate of mass return to the black hole after a disruption. Through hydrodynamical simulation, we show that aside from the full disruption of a solar mass star at the exact limit where the star is destroyed, the common assumptions used to estimate , the rate of mass return to the black hole, are largely invalid. While the analytical approximation to tidal disruption predicts that the least-centrally concentrated stars and the deepest encounters should have more quickly-peaked flares, we find that the most-centrally concentrated stars have the quickest-peaking flares, and the trend between the time of peak and the impact parameter for deeply penetrating encounters reverses beyond the critical distance at which the star is completely destroyed. We also show that the most-centrally concentrated stars produced a characteristic drop in shortly after peak when a star is only partially disrupted, with the power law index n being as extreme as –4 in the months immediately following the peak of a flare. Additionally, we find that n asymptotes to – 2.2 for both low- and high-mass stars for approximately half of all stellar disruptions. Both of these results are significantly steeper than the typically assumed n = –5/3. As these precipitous decay rates are only seen for events in which a stellar core survives the disruption, they can be used to determine if an observed tidal disruption flare produced a surviving remnant. We provide fitting formulae for four fundamental quantities of tidal disruption as functions of the star's distance to the black hole at pericenter and its stellar structure: the total mass lost, the time of peak, the accretion rate at peak, and the power-law index shortly after peak. These results should be taken into consideration when flares arising from tidal disruptions are modeled.

https://iopscience.iop.org/article/10.1088/0004-637X/767/1/25/pdf

Hydrodynamical simulations to determine the feeding rate of black holes by the tidal disruption of stars: the importance of the impact parameter and stellar structure

The disruption of stars by supermassive black holes has been linked to more than a dozen flares in the cores of galaxies out to redshift $z \sim 0.4$. Modeling these flares properly requires a prediction of the rate of mass return to the black hole after a disruption. Through hydrodynamical simulation, we show that aside from the full disruption of a solar mass star at the exact limit where the star is destroyed, the common assumptions used to estimate $\dot{M}(t)$, the rate of mass return to the black hole, are largely invalid. While the analytical approximation to tidal disruption predicts that the least-centrally concentrated stars and the deepest encounters should have more quickly-peaked flares, we find that the most-centrally concentrated stars have the quickest-peaking flares, and the trend between the time of peak and the impact parameter for deeply-penetrating encounters reverses beyond the critical distance at which the star is completely destroyed. We also show that the most-centrally concentrated stars produced a characteristic drop in $\dot{M}(t)$ shortly after peak when a star is only partially disrupted, with the power law index $n$ being as extreme as -4 in the months immediately following the peak of a flare. Additionally, we find that $n$ asymptotes to $\simeq -2.2$ for both low- and high-mass stars for approximately half of all stellar disruptions. Both of these results are significantly steeper than the typically assumed $n = -5/3$. As these precipitous decay rates are only seen for events in which a stellar core survives the disruption, they can be used to determine if an observed tidal disruption flare produced a surviving remnant. These results should be taken into consideration when flares arising from tidal disruptions are modeled. 
[abridged]

Hydrodynamical Simulations to Determine the Feeding Rate of Black Holes by the Tidal Disruption of Stars: The Importance of the Impact Parameter and Stellar Structure

Passage of Heavy Particles through Matter

Within the framework of a new local thermodynamic transcription [Ghosh, Berkowitz, and Parr, Proc. Natl. Acad. Sci. U.S.A. 81, 8028 (1984)] of ground state density‐functional theory, the electron cloud is interpreted as an inhomogeneous fluid at an effective local temperature. The correlation functions are defined and integral equations are introduced for this electron fluid along the lines of the theory of inhomogeneous classical liquids. An equation of state and a local compressibility equation are also developed. Extension to a mixture of two fluid components is explored as a means for investigating spin‐polarized cases. The formalisms broaden the scope of the hydrodynamic analogy to quantum mechanics and provide an alternative integral equation method for calculation of the electron density of many‐electron systems.

A classical fluid‐like approach to the density‐functional formalism of many‐electron systems

The evolution of the stars on the main sequence consequent to the gradual burning of the hydrogen in the central regions is examined. It is shown that, as a result of the decrease in the hydrogen content in these regions, the convective core (normally present in a star) eventually gives place to an isothermal core. It is further shown that there is an upper limit (~10 per cent) to the fraction of the total mass of hydrogen which can thus be exhausted. Some further remarks on what is to be expected beyond this point are also made.

On the Evolution of the Main-Sequence Stars.

A new hydrodynamicla model for the Schrodinger equation is discussed. The new model differs from that ofMadelung by the existence of turbulence. It follows directly from the ordinary interpretation of the quantum mechanics, by the introduction of operators for the charge and current densities and the components of the stress tensor in the one particle formalism. The model is developed for any values of the spin. The Madelung fluid corresponds to the mean motion of the special turbulent medium. The quantum potential appears as a combination of a pressure with terms arising from the turbulence. It is shown that the quantization of the motion of the Madelung fluid introduces the right kind of turbulence. The trajectories of the de Broglie-Bohm theory appear as trajectories of the mean motion of the turbulent medium.

On the hydrodynamical model of the quantum mechanics

Quantum kinematics and geometry

The difficulties of the classical theory of the electron are examined and methods to eliminate them are given. It is shown that the whole theory can be derived from a division of the total field created by a point charge in two parts, one which reacts on the generating particle and accounts for the emission of radiation, another which does not react on the praticle but acts on other particles. There are several types of motions of the particles depending on the kind of field they generate, fields which are always solutions of Maxwell's equations. Only three types of motions are, apparently, physically interesting: (a) motions with positive or negative kinetic energy in which the particles radiate, and (b) radiationless motions analogous to the stationary motions of quantum theory. It is shown that the field picture of Faraday and Maxwell must be revised because not all the electric actions between particles can be considered as arising from their interaction with a field. The whole theory of the particles and the field can be derived from an action principle and boundary conditions for the equations of motion of the particles and the field.

Classical Theory of the Point Electron

The theory of the loss of energy of a non accelerated charged particle in a material medium is investigated, using classical electrodynamics. Special attention is given to the mechanism of the loss. The results of Fermi, Halpern and Hall, Wick and A. Bohr are generalized and further extended. The points of view of action at a distance (Bohr) and field theory (Fermi) are discussed and compared. The mechanism of the emission of Cerenkov radiation is examined and the relations with the emission of acceleration radiation analysed.

Mario Schonberg

Papers

On the Evolution of the Main-Sequence Stars.

On the hydrodynamical model of the quantum mechanics

Quantum kinematics and geometry

Classical Theory of the Point Electron

Mechanism of the loss of energy by collisions in a material medium (I)