Physics of Compact Stars

Transcription

1 Physics of Compact Stars Crab nebula: Supernova 1054 Pulsars: rotating neutron stars Death of a massive star Pulsars: lab s of many-particle physics Equation of state and star structure Phase diagram of nuclear matter Rotation and accretion Cooling of neutron stars Neutrinos and gamma-ray bursts Outlook: particle astrophysics David Blaschke - IFT, University of Wroclaw - Winter Semester 2007/08

2 Example: Crab nebula and Supernova Chinese Astronomers observe Guest-Star in the vicinity of constellation Taurus 6times brighter than Venus, red-white light 1 Month visible during the day, 1 Jahr at evenings Luminosity 400 Million Suns Distance d Lightyears (ly) (when d 50 ly Life on earth would be extingished) 1731 BEVIS: Telescope observation of the SN remnants 1758 MESSIER: Catalogue of nebulae and star clusters 1844 ROSSE: Name Crab nebula because of tentacle structure 1939 DUNCAN: extrapolates back the nebula expansion Explosion of a point source 766 years ago 1942 BAADE: Star in the nebula center could be related to its origin CHANDRA (BLAU) + HUBBLE (ROT) 1948 Crab nebula one of the brightest radio sources in the sky 1968 BAADE s star identified as pulsar

3 Pulsars: Rotating Neutron stars 1967 Jocelyne BELL discovers (Nobel prize 1974 for HEWISH) pulsating radio frequency source (pulse interval: 1.34 sec; pulse duration: 0.01 sec) Today more than 1700 of such sources are known in the milky way PULSARS Pulse frequency extremely stable: T/T 1 sec/1 million years 1968 Explanation of the phenomenon GOLD as RO- TATING NEUTRON STARS, since: only Rotation explains high precision of pulses only small objects (R 10 km) can have so small pulse duations 1969 Discovery of the pulsar in the Crab nebula Connection established: SUPERNOVA - NEUTRON STAR - PULSAR 1968 Discovery of the binary Pulsar PSR by HULSE and TAYLOR (Nobel prize 1993)

4 What happens in a Supernova-Explosion? Two Szenarios after ceasing of nuclear fusion reactions in the star interior Supernova Type I (Carbon core): Explosive Burning, star is completely destroyed Supernova Type II (Iron core): Implosion due to gravitational instability, subsequent shockwave explosion and neutrino emission blast of the star envelope, star interior collapses NEUTRON STAR or BACK HOLE Neutron star-properties: Radius: R 10 km Density: ρ g/cm 3 Mass: M M = kg Rotation: Period T < 1 sec, for progenitor star T 30 d (Sun) Magnetic field: contraction increases the density of field lines dramatically H/H earth 10 12

5 Pulsars: Laboratories for Many-particle Physics Glitches: Superfluid Nuclear Matter Frequenzy f (Hz) Lecture: Astronomie II online, Notebook University Rostock (NUR) Julian Date Nature of Glitches: Vortex-Crust Unpinning suddenly smaller momet of inertia jump in Ω = dφ/dt (angular momentum conservation)

6 Phase diagram for QCD Matter at high densities 1.5 [T H =140 MeV] Temperature 0.1 QCD - Lattice Gauge Theory Big Bang CONFINEMENT CERN-SPS Hadron gas Nuclear matter RHIC, LHC (construction) AGS Brookhaven FAIR (Project) SIS Darmstadt Super- Novae Quark-Gluon-Plasma DECONFINEMENT Heavy Ion Collisions Neutron / Quark Stars 1 Baryon Density 3 Quark Matter COLOR SUPERCONDUCTIVITY -3 [n =0.16 fm ] ο Challenge to Experiments and Questions to Theory: How do Quarks get their masses (χsb)? Why are there no free Quarks and Gluons (Confinement)? Virtual Institute ( ): Dense hadronic matter and QCD phase transitions (UNIs Bielefeld, Darmstadt, Frankfurt, Giessen, Rostock, Tübingen mit GSI Darmstadt)

7 Equation of State and Stability of Compact Stars Tolman-Oppenheimer-Volkoff Equations 1. Stability: General Relativistic Hydrostatic Equilibrium dp (r) = G m(r)ε(r) ( 1 + P (r) dr r 2 ε(r) ) ( 1 + 4πr3 P (r) m(r) ) ( 1 2Gm(r) ) 1 r NEWTON EINSTEIN CORRECTIONS GENERAL REL. THEORY 2. Mass Distribution: m(r) = R 0 ε(r) 4π r 2 dr P [MeV fm -3 ] Flow constraint DBHF η D = 0.92, η V = 0.0 η D = 1.00, η V = 0.5 η D = 1.03, η V = 0.5 η D = 1.02, η V = n [fm -3 ] M [M sun ] causality constraint 4U U DBHF (Bonn A) η D = 0.92, η V = 0.0 η D = 1.00, η V = 0.5 η D = 1.02, η V = 0.5 η D = 1.03, η V = 0.5 η D = 1.00, η V = 0.0 RX J R [km] 0.7 XTE J EXO z = 0.1

8 Ω Rotation and Star Structure Axially symmetric solutions of the EINSTEINequations for compact stars show:: Deformation (Excentricity) r [km] N B =1.3 N O H R e R p N B =1.55 N O H R e R p N B =1.8 N O H M R p R e new density distribution (centrifugal forces) further general relativity effects 3 M Ω [khz] Q M Ω [khz] Q Ω [khz] Phase transition to Quark matter depends on Mass (Baryon number N) and Angular velocity (Ω = dφ/dt) of the Star! Phase diagram (Ω N plane) = visualizes observable Signals: Braking index (spin-down) Population-clustering (accretion) 1Moment of inertia Phase transition! Ω [khz] No Stationary Rotating Stars Hadronic Stars Quark Core Stars Black Holes N/N. N

9 Low-mass X-ray Binary (LMXB) LMXB s show: Accretion (N - Evolution) X-ray bursts with quasiperiodic Brightness Oscillations (QPO s) further general rel. effects (ISCO) Ω {khz] No Stationary Rotating Stars Ω max (N) Hadronic Stars over 100 million years about 60 million years N crit (Ω) 0.6 TG 1.0 TG Quark Core Stars N max (Ω) N [N sun ] Black Holes ν [khz] Phase transition Signal: Population clustering at N crit (Ω) QPO-Phenomenon gives informations about: Mass-radius relation Rotation frequency Ω N plane Hertzsprung-Russell- Diagram for QPO s!

10 log(t s [K]) Cooling of Compact Stars-Results Cooling of Hybrid stars with 2SC Quark core HJ (Y - 3P 2 *0.1) with K = 240 MeV with Med. effects, our crust, Gaussian FF PSR J in 3C58 Crab RX J E RX J CTA Vela PSR Geminga PSR RX J critical ν e T =40 MeV ν e ν e QM ν e ν e ν e ν e T = 0 2SC Neutrinos carry energy off the star = Cooling evolution given by dt (t) dt = ɛ + j=urca,... ɛj ν i=q,e,,... ci V log(t[yr]) Enhanced Cooling by URCA Signal 2SC+X phase, X 30 kev Pulsar in 3C58 - candidate for a Quark Star? Grigorian, DB, Voskresensky: Phys. Rev. C 71 (2005) d - ν e - u

11 Magnetic Quark Star: Neutrino Beam Gamma-Ray-Burst Neutrinos trapped in a star when temperature T > 1 MeV ( K) mean free path R 2SC quark matter core with magnetic vortices (B G) Beamed emission neutrinos, E erg vortex superconductor R star surface Conversion of neutrinos photons: Gamma-Ray Burst (?) θ ν G G G ν,ν ν,ν λ ν ν ν + e e L [erg/s] 1e+53 1e+52 1e+51 1e+50 B = G B = G B = G B = G B = G conversion T [MeV] θ ν [grad] t [s]

12 Puzzling Compact Star Phenomena - Quark Star Candidates? Quasiperiodic Brightness Oscillations (QPO s) in Low-mass X-Ray Binaries (LMXB s) Limits for Mass - Radius - Relation 2 M too large mass for quark stars? Rossi-XTE LMXB Gamma-Ray Bursts (GRB), extragalactic, extremely bright, Connection to Supernova Explosions Which Engine erg? INTEGRAL Isolated X-ray source (RX J18565), 17 km radiation radius too big for a Neutron Star? HUBBLE GRB RX J Pulsar in Supernova Remnant (3C58; AD 1181) with Temperature T = 10 6 K too cold for a Neutron Star? CHANDRA 3C58

13 Wide variety of supernovas - progenitor mass dependence

14 Supernova Collapse in the Phase Diagram 10 2 Supernova evolution in the phase diagram temperature T [MeV] 10 1 Nuclear matter 2SC density ρ [g cm -3 ]

15 Supernova Collapse in the Phase Diagram (II) 10 2 Supernova evolution in the phase diagram temperature T [MeV] 10 1 Nuclear matter 15 M sun (Harald Dimmelmeier) 2SC density ρ [g cm -3 ]

16 Supernova Collapse in the Phase Diagram M sun (Tobias Fischer) temperature T [MeV] M sun (Harald Dimmelmeier) density ρ [g cm -3 ]

17 The case of SN2006gy

18 The case of SN2006gy - a Quarknova? Discovery: Sept. 18, 2006 in NGC 1260 (Perseus) Distance: 72 Mpc=238 Mill. Ly (Smith et al.: astro-ph/ ) Light curve: 70 days rise time Energy release: erg= 10 bethe Progenitor star: 150 M? Engine: Quark-star formation? (Leahy & Ouyed: [astro-ph])

19 Equation of State for Supernova Applications Supernova 1987A - 20 years later: Big mystery of rings! Double degenerate core in common envelope? 2.14 ms periodic signal Explanation for 99% of GRB? Middleditch, [astro-ph]

20 Equation of State for Supernova Applications What has happened here?? Supernova 1987A - 20 years later: Big mystery of rings! Double degenerate core in common envelope? 2.14 ms periodic signal Explanation for 99% of GRB? Middleditch, [astro-ph]