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Home , Chandrasekhar limit, White dwarf

Specialist Course - Compact Objects In

White Dwarfs, , and Black Holes

Maurizio Falanga [email protected]

Einführung und Überblick: Donnerstag, 20. Februar 2020 Organisation der Vorlesung

Zeit & Ort: Donnerstag 10:15 – 12:00 Uhr; Physik, Hörsaal B78

Voraussetzung (ECTS 4):

• regelmässige und aktive Teilnahme an der Vorlesung • regelmässige und aktive Teilnahme an den Übungen

Webseite:

Einführung und Überblick 19. September 2017 Lectures

General introduction to high energy equations, Equation of States dwarfs, npe-gas, Equation of states for WD Equation of States for dense Neutron Stars observational signatures , Radio, X-ray Conditions for flow through an disks and or wind Single aspect of Black holes observational aspects Radiation processes Exercises

- 6 Exercises for different topics to solve during the whole period

- One Numerical Project to work on. Write a simple code, using only analytical equations, to trace (in the ) the photons emitted around a as seen from an distant observer. Objectives

Formation and observation of compact stars and stellar black holes in the context of .

Astrophysical phenomena related to compact objects.

Properties and description of dense matter.

Simple applications of the theory of relativity. Literatur

Frank, King & Raine: Accretion Power in Astrophysics Rosswog & Brüggen: Introduction to High-Energy Astrophysics Shapiro & Teukolsky: Black Holes, White Dwarfs, and Neutron Stars

Seward & Charles: Exploring the X-ray Rybicki & Lightman: Radiative Processes in Astrophysics Chandrasekhar: The Mathematical Theory of Black Holes Sternentwicklung S. Chandrasekhar 1910-1995 A massive can collapse into something denser WD (1930) R. Oppenheimer & H. Snyder predict that massive stars can collapse into black holes (1939)

Weisse Zwerge White Dwarfs:

• 1844: F. Bessel noticed that had a slight back and forth motion, as if it was orbiting an unseen object. In 1863, the astronomer A. Clark spotted this mysterious object (Radius, period). This companion star was later determined to be a (Radius, Mass). Types of CV binaries: Magnetic Cataclysmic Variables Non MCVs B ~ 108 –106 G

Polars Intermediate Polars Classical/Dwarf Novae (Prototype AM Her) P ~ 1-10 hrs orb Energy Sources: Synchronous Rotation Asynchronous Rotation CN: nuclear burning DN: through Pspin = Porb Pspin « Porb Porb (P) < Porb (IP)

2 Lacc = ηMc η ~ 0.7% (CV); ~ 20% (NS) (For a review see B. Warner 1995) Neutronenstern Radio in the 30’s-60’s

Karl Jansky 1933

3C273 Discovery (1961-63) Quasi-Stellar Radio Sources as the most energetic and distant members of a class of objects 1967 Radio Signals from the Sky Period of 1.337 s 1.3372866576 s - They soon realized that the best clocks of the time were not accurate enough to time the object. It seemed very unnatural to receive such a perfectly regular signal from space! - It could originate from extra terrestrial intelligence? LGM-1 (Little Green Men)

Jocelyn Bell (1943-) S. Chandrasekhar (1910-1995)

A massive star can collapse into something denser (1930). He was awarded the 1983 for this fundamental prediction!

James Chadwick (1891-1974)

In 1932, James Chadwick, then at the Cavendish Laboratory in Cambridge, England, discovers the neutron. He got the Nobel physics prize in 1935.

Fritz Zwicky (1898 –1974) In 1934, F. Zwicky and W. Baade and that a stellar collapse of a heavy star during a event should lead to the formation of a dense core of

(NS) at theM. center Falanga of the SN remnant. During the course of the next few months, J. Bell discovered 3 more pulsating radio sources (or pulsars). These pulsars were proposed to be rapidly rotating neutron stars.

Anthony Hewish, won the Nobel Prize in Physics for the discovery in 1974. PULSARS are NEUTRON STARS

Properties of neutron stars: R ~ 10 km ρ ~1014g/cm3

M ~ 1.4 Msun

- Magnetic dipole - Electromagnetic radiation - slowdown

Core collapse of an evolved star • collapse => conservation of => fast spinning ! • Stellar core collapse => conservation of magnetic flux => highly magnetized neutron star

• Pacini (1967) proposed the existence of a highly magnetized, rapidly spinning neutron star as the power source of the . This would radiate a very powerful EM wave with the rotational frequency of the star. This is below the frequency of the nebula, therefore all this energy will be absorbed and re-radiated by the plasma of the nebula. In 1968, at the height of the “pulsar fever”, giant radio pulses originating in the Crab Nebula were detected.1968: The discovery of These extremely short bursts (~33 ms) proved the existence PSRof a pulsar B0531+21 at the center of the Nebula. (Crab Pulsar)

(This is the compact radio source detected by Hewish and Okoye in 1964) 1054

PSR 0531+21 Schwarze Löcher The existence of “dark stars” (in Newtonian mechanics) Escape Velocity

1/2 Isaac Newton (1643-1727) 2GM V = R

Earth: 11.2 km/s Moon: 2.3 km/s : 600 km/s John Michell (1724–1793)

A Treatise of the System of the World, London (1728)

Pierre-Simon Laplace (1749–1827) K. Schwarzschild 1873-1916

Finds black holes as a solution to Einstein’s equations (1916) The Rs = 2 M

R. P. Kerr 1934 - Finds the solution for rotating black holes (1963)

J. A. Wheeler 1967 Black Holes 1911-2008 Black Escape velocity c Hole singularity in space-time No Hair Theorem BH have NO HAIR

Black Holes

J. A. Wheeler X-ray Astronomy 1962

1972

1970

§ Bright X-ray emission § Rapid X-ray variability § § § Orbits,5.6days,an unseen optically (but bright X-ray)object 30M

The companion hasa massbetween of~10M ¤

Blue supergiant main-sequence star (optically bright, X-raydim) Optical Astronomy X-ray Binary System

Sloan Digital Sky Survey ¤

Cygnus X-1

What is it?

§ A would be easily seen § A main-sequence star would be seen with a little effort

§ Can’t be a White Dwarf because M > 1.4 M¤

§ Can’t be a Neutron star because M > 3 M¤

By elimination, we are left with a Black Hole

§ The companion has a mass between of ~ 10 M¤ Black Hole in our Galactic Center ?

NIR Evidences of a SM-BH at the GC

NIR adaptive optics at VLT & Keck h Proper motions of the stars of the central cluster h Orbital parameters of the closest star to the GC: P ≈ 15.2 yr, V ≈ 5000 km s-1 h Dynamical center in Sgr A*

h 6 Enclosed Dark Mass ≈ 3-4 10 M¤

within 124 AU = 17 l. h. ≈ 2000 RS

Types of Black Holes

Stellar-mass 31 Must be at least 3 solar (~10 kg)

Intermediate mass A few thousand to a few tens of thousands of solar masses; possibly the agglomeration of holes

Supermassive Millions to billions of solar masses; located in the centers of galaxies

We cannot see black holes directly, but their influence on the matter around them reveals their presence Disk Accretion Shakura & Sunyaev, 1973, A&A

Artist impression

Energy released onto the Black Hole as X-ray

M G MNS 35 38 -1 LX ≈ ~10 -10 erg s RNS Mass determination in binary systems (Kepler’s Law) 2π a 3/2 P = 1/2 1/2 a: semi-major axis G [m +m ] 1 2 P: orbital period i: orbital inclination angle 2πa1 v1 = P , m1a1 = m2a2, a = a1 + a2 v1,obs: line of sight speed Center of the Gravity 2πa m2 v = a1 1 P(m1 +m2 ) 2πa m sin i v = v sini = 2 1,obs 1 P(m1 +m2 ) a2 3/2 3/2 3/2 3/2 3/2 P (m1 +m2 ) v1,obs P (m1 +m2 ) v1,obs P = 1/2 3/2 1/2 1/2 = 1/2 3/2 1/2 (2π ) (m2 sin i) G [m1 +m2 ] (2π ) (m2 sin i) G

3 3 Pv1,obs (m2 sin i) 2πG = 2 (m1 +m2 )

With the mass ratio (m1/m2); we still need the orbital inclination in order to determine the masses individually. € ©http://mc2.gulf-pixels.com/ 35

What is X-ray?

• X-ray = high-energy photon o hν = 0.1 keV – 100 keV o λ = 0.1 – 100Å (λ1keV = 12.4Å) 6 10 7 o kT = 10 – 10 K (kT1keV = 10 K)

• We can see o Extremely high temperature o Non-thermal particle acceleration o Atomic process Radiation processes

Bremsstrahlung:

Synchrotron radiation:

Compton Scattering: Multi temperature and post-shock model for CVs

Magnetic Field NS geometry of the emission region

The plasma is heated by the θ accretion shock as the material B ~ 108 G collimated by the hotspot on to Seed photons from the hotspot the surface. The seed photons for Comptonization are provided by the hotspot.

XTE J1807-294 Rm

Thermal disk emission

Thermal Comptonization in plasma of Temperature ~ 40 keV Detected in 1969 Cen X-4 with Discovery paper 3U 1820-30 Vela 5b (Belian et al. 1972) with ANS (Grindlay et al. 1976)

Type of X-ray Bursts Kuulkers, in ’t Zand & Lasota 2009 Falanga et al. 2008 M

Iron reflection line M Relativistic line

Accretion disk model X-ray Sources in the observed with INTEGRAL

Over 700 hard X-ray sources ranging from CV to AGN 6 White dwarfs: R~10,000 km, Vesc~0.02 c, density~ 10 g/cc 14 Neutron stars: R~15 km, Vesc~0.32 c, density~ 10 g/cc

Schwarzschild radius = 2.95 km M/Mo Efficiency of energy production 6% to 42%.

Disk Accretion Shakura & Sunyaev, 1973, A&A

Artist impression

Energy released onto the Black Hole as X-ray Luminosity

M G MNS 35 38 -1 LX ≈ ~10 -10 erg s RNS Types of Black Holes

Stellar-mass 31 Must be at least 3 solar masses (~10 kg)

Intermediate mass A few thousand to a few tens of thousands of solar masses; possibly the agglomeration of stellar mass holes

Supermassive Millions to billions of solar masses; located in the centers of galaxies

We cannot see black holes directly, but their influence on the matter around them reveals their presence