Relativistic Astrophysics Neutron Stars, Black Holes & Grav. W. ... A brief description of the course

Relativistic Astrophysics Neutron Stars, Black Holes & Grav. Waves... A brief description of the course May 2, 2009

Structure of the Course Introduction to General Theory of Relativity (2-3 weeks) Gravitational Collapse (1 week) Neutron Stars (2-3 weeks) Black Holes (2-3 weeks) Gravitational Waves (2-3 weeks)

Introduction to General Theory of Relativity Short Introduction to Tensors What is General Relativity and Einstein s equations Three solutions of Einstein s equations with astrophysical interest (Schwarschild, Kerr, TOV) Orbits in the vicinity of black-holes

Gravitational Collapse A typical supernova occurs when the core of a massive star runs out of nuclear fuel and collapses under its own gravity to form an ultra-dense object known as a neutron star. The newborn neutron star compresses and then rebounds, triggering a shock wave that ploughs through the star s gaseous outer layers and blows the star to smithereens. Figure: Supernova explosion Figure: Crab Nebula Figure: Supernova 1987a, photo taken by the Hubble telescope in 1995

Gravitational Collapse Supernovae result from the explosive death of a star and are classified as two types. Type Ia supernovae occur in binary star systems in which gas from one star falls onto a white dwarf with a mass close to the Chandrasekhar critical mass and causes it to explode. The explosion is caused by the ignition of runaway thermo-nuclear reactions under degenerate matter conditions. Type II supernovae occur in stars at least ten times more massive than our Sun, which suffer runaway thermo-nuclear reactions at the end of their lives, leading to explosions. Such explosions can be either total (no solid remnant) or may leave behind a rapidly spinning neutron star (a pulsar) or a black hole.

Neutron Stars A neutron star is a type of remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons. Neutron stars are very hot and are supported against further collapse because of the Pauli exclusion principle. This principle states that no two neutrons (or any other fermionic particle) can occupy the same quantum state simultaneously. A typical NS has a mass between 1.2-2.1 M, with a corresponding radius of 9-15 km and central densities around 10 15 gr/cm 3. Figure: Pulsar Figure: LMXB Figure: Magnetar

Neutron Stars Equilibrium configurations in GR How to construct a relativistic star White Dwarf Stars Neutron Stars pure neutron stars more complicated equation of state maximum mass of NS rotation, pulsars Magnetic fields on NS & Magnetars Binary Pulsars Low-mass X-ray binaries (LMXB) Intermediate-mass X-ray binaries (IMXB) High-mass X-ray binaries (HMXB) Accretion-powered pulsar ( X-ray pulsar ) Exotic Stars

Black Holes Black holes are among the most intriguing objects in modern physics. They power quasars and other active galactic nuclei and also provide key insights into quantum gravity. We will review the observational evidence for black holes and briefly discuss some of their properties. We will also issues related to black-hole thermodynamics. Figure: BH Spacetime Figure: BHs have no hair Figure: BH in action

Black Holes What are the black holes according to GR Observational evidence for BHs The maximum mass of neutron stars Observational signatures of black holes Supermassive black holes in galactic nuclei Black holes in x-ray binaries Conclusive evidence for black holes Quantum Black Holes

Gravitational Waves Gravitational forces cannot be transmitted or communicated faster than light. This means that when the gravitational field of an object changes, the information about these changes will take a finite time to reach other objects. These ripples are called gravitational radiation or gravitational waves. Figure: Gravitational Waves Figure: Merging Neutron Stars Figure: Merging Neutron Stars

Gravitational Waves What are the gravitational waves How do they produced Astrophysical Sources of GWs Binary Systems Supernova Collapse Isolated Neutron Stars Early Universe Detection of Gravitational Waves Figure: Schematic GW Detector Figure: Virgo & LISA