RELATIVISTIC ASTROPHYSICS

Second cycle degree in PHYSICS

Campus: PADOVA

Language: English

Teaching period: Second Semester

Lecturer: ROBERTO TUROLLA

Number of ECTS credits allocated: 6


Syllabus
Prerequisites: Classical electrodynamics, special relativity, general astronomy and astrophysics
Examination methods: Oral examination
Course unit contents: Compact objects. Late stages of stellar evolution, core-collapse supernovae. White dwarfs, neutron stars and black holes.

General relativity. The vacuum Schwarzschild solution and its properties. Geodesic motion in the Schwarzschild spacetime. Interior Schwarzschild solution, hydrostatic equilibrium configurations, the Tolman-Oppenheimer-Volkoff equation. The Kerr solution (basics).

Degenerate systems. Quantum statistics (brief overview). Equation of state for a completely degenerate gas; the non-relativistic and ultra-relativistic limits. The Chandrasekhar mass.

Matter-radiation interaction. The radiation field. Emission, absorption and scattering. The radiative transfer equation. Optical depth. Simple solutions to the transfer equation: radiative diffusion and free streaming. Radiative processes: electron scattering and free-free. The Eddington limit.

Accretion onto compact objects. Spherical accretion, the Bondi-Hoyle solution. Compact objects in bynary systems. The Roche lobe geometry. Wind- and Roche lobe-fed accretion. Accretion discs. The standard disc model (alpha-disc). Radiation spectrum from an alpha-disc.

Neutron stars. Magnetic field and rotation. Magneto-rotational braking and the period evolution. Estimate of the magnetic field and of the age from the period and the period derivative. The P-Pdot diagram. Magnetosphere, light cylinder. Goldreich-Julian currents. The Alfven radius, column accretion onto magnetized neutron stars. Internal structure of a neutron star. Neutronization. Neutron star cooling. Neutrino cooling, URCA and modified URCA. Radiative cooling. Cooling curves.