Nucleosynthesis Explosions Final Stages of Stellar For Take Away

Final Stages of supernovae and the synthesis of heavy nuclei

Benjamin Klein

University of Karlsruhe

06.XII.2006 Seminar on Astroparticle Physics - Cosmic Rays Supernova Explosions Final Stages of Stellar Evolution For Take Away

Introduction

What happens to which run out of fuel? What are supernova explosions and which different types exist? Where do heavy elements come from? Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Outline

1 Nucleosynthesis Revision of Nucleosynthesis up to Nuclear Synthesis of Heavy Elements

2 Supernova Explosions Dwarfs Classification of Supernovae

3 Final Stages of Stellar Evolution Stars Black Holes Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Outline

1 Nucleosynthesis Revision of Nucleosynthesis up to Iron Nuclear Synthesis of Heavy Elements

2 Supernova Explosions White Dwarfs Classification of Supernovae

3 Final Stages of Stellar Evolution Neutron Stars Black Holes Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Outline

1 Nucleosynthesis Revision of Nucleosynthesis up to Iron Nuclear Synthesis of Heavy Elements

2 Supernova Explosions White Dwarfs Classification of Supernovae

3 Final Stages of Stellar Evolution Neutron Stars Black Holes Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Outline

1 Nucleosynthesis Revision of Nucleosynthesis up to Iron Nuclear Synthesis of Heavy Elements

2 Supernova Explosions White Dwarfs Classification of Supernovae

3 Final Stages of Stellar Evolution Neutron Stars Black Holes Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Primordial Nucleosynthesis

within the first 3 minutes after the synthesis of elements neutron/ ratio of 1:7 most → He most remaining → H only traces of heavier elements nuclear magic numbers A = 5 and A = 8 photodissociation of heavier elements Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Stellar Nucleosynthesis

synthesis of elements up to iron proton-proton chain CNO cycle nuclear burning in different zones onion structure Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Outline

1 Nucleosynthesis Revision of Nucleosynthesis up to Iron Nuclear Synthesis of Heavy Elements

2 Supernova Explosions White Dwarfs Classification of Supernovae

3 Final Stages of Stellar Evolution Neutron Stars Black Holes Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away s-process (1)

process of neutrons preferentially captured by heavy nuclei base material eg. iron nucleus becomes instable → β−-decay slow-process 5 11 neutrons “low” neutron flux (10 − 10 s·cm2 ) “low” temperatures (∼ 3, 000, 000K) β− decay before next neutron is captured conditions met in stars Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away s-process (2)

moving along the Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away s-process (3) Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away s-process (4) limitations of the s-process

not all heavy elements can be synthesized in the s-process heavy nuclei, eg. thorium or uranium, decay several times before repeated neutron capture ends in bismuth cycle Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away s-process (5) at FZK

research group of Dr. Käpperle at FZK measurements of cross sections for neutron capture ratification of models for red giant stars Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away r-process (1)

rapid-process 22 neutrons high neutron flux (∼ 10 cm2·s ) high temperatures multiple neutrons captured before β−-decay possible places where r-process could take place supernovae II (T ∼ 109K ) collision of two neutron stars abundance of r-process elements indicates that... only small quantity of supernovae returns elements to the outside every supernovae exposes only a small fraction of its synthesis products to the outside Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away r-process (2) processes slowing down the r-process

heavy unstable because of spontaneous fission (A ' 270) → r-process ends

neutron drip line → separation En = 0 closed neutron shells at N = 50, 82, 126 probability of capture sinks confirmation: higher abundance for this neutron numbers Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away r-process (3)

magic neutron numbers: N = 82, N = 126 s-process: A = 138 (Barium) A = 208 (Lead) r-process: A = 130 (Cadmium) A = 195 (Thulium) Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

(r)p-process

have to overcome p-process process (γ, n), (γ, α) supernovae temperatures T ∼ 3 · 109K p-only isotopes, eg. 190Pt(Platinum), 168Yb(Ytterbium) rp-process proton captures onto seed nuclei rich environment surface of a or neutron Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Neutron Capture Processes Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Outline

1 Nucleosynthesis Revision of Nucleosynthesis up to Iron Nuclear Synthesis of Heavy Elements

2 Supernova Explosions White Dwarfs Classification of Supernovae

3 Final Stages of Stellar Evolution Neutron Stars Black Holes Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

White Dwarfs (1)

intermediate state of a dying low or medium mass star inner core of former red consists mostly of and not heavy enough to fuse carbon after fusion stops only degeneration pressure supports core against gravitational collaps

pdegeneration ∼ pgravitation if Mstar ≤ 1.4 · M ≡ MChandrasekhar if Mstar > MChandrasekhar → supernova Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

White Dwarfs (2)

approximately the size of the Earth

0.5 − 0.6M ρ ∼ 9 kg 10 m3 R ∝ 1 white dwarf M1/3 extremely hot (∼ 20, 000K) with small surface →∼ 25 billion years to cool down final state: Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Outline

1 Nucleosynthesis Revision of Nucleosynthesis up to Iron Nuclear Synthesis of Heavy Elements

2 Supernova Explosions White Dwarfs Classification of Supernovae

3 Final Stages of Stellar Evolution Neutron Stars Black Holes Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Supernovae

stellar explosion which involves the whole star two mechanisms

stars with Mstar > 8 · M → after of nuclear fuel → core collapse white dwarfs with Mstar < 8 · M in binary system with red giant → of matter → multiple explosions → supernova 20 ± 8 supernovae per millenium in the (2/3 visible) Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Classification

classification in 1939 by Rudolph Minkowski two types with subtypes by chemical experiments in their spectra SN Type I: without hydrogen Balmer line Ia: no hydrogen, strong Ib: weak hydrogen, strong Ic: no hydrogen, no helium, weak silicon SN Type II: with hydrogen Balmer line Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Naming of Supernovae

prefix “SN” followed by year of discovery first 26 supernovae upper case letter from A to Z following combination of lower case letters aa to zz eg. SN1987A was the first observed supernova in 1987 last supernova in 2005: SN2005nc november 2006: SN2006ot Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Novae

close binary system of a white dwarf and a red giant cataclysmic nuclear explosion caused by accretion of hydrogen hydrogen compacts on the surface of the white dwarf under high pressure and temperature fusion (CNO-cycle) heavier fusion products remain on the surface remaining gas is blown away from the surface Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Supernovae Ia (1)

same preconditions as for nova heavy elements as fusion products of novae remain on the surface → increasing mass

mass slightly under MChandrasekhar → reaction of carbon and oxygen white dwarf supported against by quantum degeneray pressure no expansion → no cooling unregulated fusion thermonuclear supernova Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Supernovae Ia (2)

no remaining compact massive object km companion star escapes with orbital velocity ∼ 100 s → “runaway star” Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Supernovae Ia (3) Supernova Cosmology Project

SN Ia always same absolute → standard candles Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Supernovae II

hydrogen Balmer line visible stars ∼ 8 − 30 · M stars heavy enough for fusion up to iron reach always (∼ 0.9M ) core collapse Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Core Collapse (1) Collapse Accelerated by Two Processes

photodisintegration photodissociation of iron nuclei by high energy γ-rays γ +56 Fe → 134He + 4n γ +4 He → 2p+ + 2n high binding energy of iron → requires energy radiation pressure decreases inverse β-decay − e + p → n + νe loss of free decreasing pressure Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Core Collapse (2)

core collapse takes only some milliseconds in a distance of 20-50 km of the center pressure not high enough for matter to respond

vmatter > vsound because of photodissociation mostly neutrons in the inner core → degeneration pressure → core almost instantanously incompressible shockwave reflected Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Core Collapse (3) Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Core Collapse (4)

high temperature gas & neutrons from the center → r-process Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Core Collapse (5) Cooling of the Inner Core

electron/positron pair production 2γ → e+ + e− high cross section → cannot escape re-annihilation /antineutrino pair production 2γ → ν +ν ¯ can finally escape → cooling liberated gravitational binding energy 99% in 1% kinetic energy of explosion 0.01% photons 53 19 neutrino L ∼ 3 · 10 erg/3sec ∼ 3 · 10 L Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Core Collapse (5) Observation of Supernovae

observation of neutrinos before optical detection scattering of ν and γ cross section σγ  σν SN1987A: Kamiokande II SuperNova Early Warning System (SNEWS) Super-Kamiokande LVD SNO AMANDA Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Subtypes of Supernovae II

supernovae II-P high ejected mass and velocity of shell decreasing luminosity compensated by fast expanding shell light curve shows plateau domain maximum luminosity strongly connected to radius of progenitor star → peak value of luminosity widely spread supernovae II-L low expansion velocity linear decreasing luminosity marginally spread peak luminosity Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Supernovae Ib/Ic

stars with mass > 30 · M Wolf Rayet phase core collapse as in SN II supernova Ib/Ic Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Outline

1 Nucleosynthesis Revision of Nucleosynthesis up to Iron Nuclear Synthesis of Heavy Elements

2 Supernova Explosions White Dwarfs Classification of Supernovae

3 Final Stages of Stellar Evolution Neutron Stars Black Holes Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Neutron Stars (1)

neutron stars proposed by Walter Baade and Fritz Zwickly in 1933

mass of 1.35 − 2.1M 6 radius ∼ 10 − 20km (R ∼ 10 km) high rotation speed (∼ 1/700 − 30sec) because angular momentum conserved escape velocity ∼ 150, 000km/s supported by neutron degeneration pressure slowing down between 10−10 − 10−21sec/rotation Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Neutron Stars (2) Different Types Of Neutron Stars

x-ray bursters in binary system accreting matter from companion star, causing irregular X-ray bursts neutron star emitting pulses of radiation neutron star with extremly strong magnetic fields magnetic fields of ∼ 100GT rotation period ∼ 5 − 12sec Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Pulsars (1)

first discovered by Jocelyn Bell Burnell and Antony Hewish in 1967, PSR1919+21 “LGM-1” very regular periodical signal detectable radio array → pulses of radiation solution: rotating neutron stars sources of energy rotation powered pulsars accretion powered pulsars → X-rays magnetic powered pulsars Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Pulsars (2) Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Pulsars (3) Millisecond Pulsars

in 1982 discovery of millisecond pulsars “MSPs” rotation periode ∼ 1.6ms extraordinarily stable rotation → astronomical clocks measurement of gravitational waves Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Crab Nebula (1)

observed by John Bevis in 1731, Earl of Rosse in the 1840s SN1054 pulsar in its centre (∼ 30rounds/sec) radiation from gamma rays to radio waves

progenitor star 8 − 12M Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Crab Nebula (2)

filaments remnants of the progenitor star’s atmosphere ionised helium and hydrogen, carbon, oxygen, nitrogen, iron, , sulphur density ∼ 1, 300particles/cm3 diffuse blue region → synchroton radiation pulsar → strong magnetic field radiation used for studying objects that occult it Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Crab Nebula (3) Studying Objects that Occult the Crab Nebula Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Crab Nebula (4) Path of Titan in 2003 Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Outline

1 Nucleosynthesis Revision of Nucleosynthesis up to Iron Nuclear Synthesis of Heavy Elements

2 Supernova Explosions White Dwarfs Classification of Supernovae

3 Final Stages of Stellar Evolution Neutron Stars Black Holes Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Black Holes (1)

body so massive that light can’t escape concept by English geologist John Michell in 1784

collapse of neutron star > 3 · M → Tolman-Oppenheimer-Volkoff limit = 2GM Schwarzschild Radius RSchwarzschild c2 event horizon theory of general relativity curvature → ∞ singularity at the center Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Black Holes (2) Light Cone Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

Black Holes (3) Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away Black Holes (4) Supermassive Black Holes

supermassive black holes in center of most → collapse of dense cluster of stars large amouts of mass accreting onto stellar “seed” fusion of smaller black holes 9 masses up to 10 · M jets acceleration of high energetic cosmic rays Nucleosynthesis Supernova Explosions Final Stages of Stellar Evolution For Take Away

For Take Away

Diffrent types of supernovae: core collapse vs. thermonuclear supernovae Supernovae Ia used as cosmic standard candles. Final stages of stellar evolution are black dwarfs, neutron stars and black holes, depending on the mass of the star. Heavy elements produced in the s-process in red giant stars and in the r-process in supernova explosions.