Relativistic Astrophysics Neutron Stars, Black Holes ...kokkotas/... · Black Holes Black holes are...

Relativistic AstrophysicsNeutron Stars, Black Holes & Grav. Waves

...A brief description of the course

Kostas Kokkotas

May 2, 2009

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

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 astrophysicalinterest (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: Supernovaexplosion Figure: Crab Nebula

Figure: Supernova 1987a,photo taken by the Hubbletelescope in 1995

Gravitational Collapse

Supernovae result from the explosive death of a star and are classified astwo types.Type Ia supernovae occur in binary star systems in which gas from onestar falls onto a white dwarf with a mass close to the Chandrasekharcritical mass and causes it to explode. The explosion is caused by theignition of runaway thermo-nuclear reactions under degenerate matterconditions.Type II supernovae occur in stars at least ten times more massive thanour Sun, which suffer runaway thermo-nuclear reactions at the end oftheir lives, leading to explosions. Such explosions can be either total (nosolid remnant) or may leave behind a rapidly spinning neutron star (apulsar) or a black hole.

Figure: SN2008D :Swift satellite observed the first moments of asupernova explosion as it happens

Neutron Stars

• A neutron star is a type of remnant that can result from thegravitational collapse of a massive star during a Type II, Type Ib or TypeIc supernova event. Such stars are composed almost entirely of neutrons.• Neutron stars are very hot and are supported against further collapsebecause of the Pauli exclusion principle. This principle states that no twoneutrons (or any other fermionic particle) can occupy the same quantumstate simultaneously.• A typical NS has a mass between 1.2 - 2.1 M�, with a correspondingradius of 9 - 15 km and central densities around ∼ 1015gr/cm3.

Figure: PulsarFigure: LMXB

Figure: MagnetarKostas Kokkotas Relativistic Astrophysics Neutron Stars, Black Holes & Grav. Waves ... A brief description of the course

Neutron Stars

Equilibrium configurations in GR

How to construct a relativistic star

White Dwarf Stars

Neutron Stars

pure neutron starsmore complicated equation of statemaximum mass of NSrotation, pulsarsMagnetic 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

Neutron Stars

White Dwarf Stars

Neutron Stars

Binary Pulsars

Exotic Stars

Neutron Stars

White Dwarf Stars

Neutron Stars

Binary Pulsars

Exotic Stars

Neutron Stars

White Dwarf Stars

Neutron Stars

Binary Pulsars

Exotic Stars

Neutron Stars

White Dwarf Stars

Neutron Stars

Binary Pulsars

Exotic Stars

Neutron Stars

White Dwarf Stars

Neutron Stars

Binary Pulsars

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 SpacetimeFigure: BHs have nohair

Figure: BH in action

Black Holes

What are the black holes according to GR

Observational evidence for BHs

The maximum mass of neutron starsObservational signatures of black holesSupermassive black holes in galactic nucleiBlack holes in x-ray binariesConclusive 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: GravitationalWaves Figure: Merging Neutron

Figure: Merging NeutronStars

Gravitational Waves

What are the gravitational wavesHow do they producedAstrophysical Sources of GWs

Binary SystemsSupernova CollapseIsolated Neutron StarsEarly Universe

Detection of Gravitational Waves

Figure: Schematic GW Detector Figure: Virgo & LISA

Gravitational Waves

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