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COOLING OF N EUTRON ST A R S

Explore the primitive and complicated cooling theory of neutron stars, including neutrino emission, superfluidity, and more. Learn about key collaborators and observations in this fascinating field of study.

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COOLING OF N EUTRON ST A R S

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  1. COOLING OF NEUTRON STARS D.G.Yakovlev Ioffe Physical Technical Institute, St.-Petersburg, Russia • Introduction • Neutrino emission • Cooling theory • Phenomenological concept • Theory and observation • Connections • Conclusions • Main collaborators: • A.D. Kaminker, Ioffe Institute • A.Y. Potekhin, Ioffe Institute Huntsville – May – 2009

  2. Cooling Theory: Primitive and complicated at once

  3. OVERALL STRUCTURE OF A NEUTRON STAR • Four main layers: • Outer crust • Inner crust • Outer core • Inner core • The main mystery: • Composition of the core+ • The pressure of dense • matter= • The problem of • equation of state (EOS)

  4. Basic Ideas

  5. Main cooling regulators Neutrino emission in neutron star cores EOS, composition of matter Superfluidity Heat content and conduction in cores Heat capacity Thermal conductivity Thermal conduction in heat blanketing envelopes Thermal conductivity Chemical composition Magnetic field Internal heat sources (for old stars and magnetars) Viscous dissipation of rotational energy Ohmic decay of magnetic fields, ect.

  6. Strongest Neutrino Emission: Direct Urca Process Lattimer, Pethick, Prakash, Haensel (1991) Is forbidden in outer core by momentum conservation: In inner cores of massive stars Threshold: ~ Similar processes with muons Similar processes with hyperons, e.g.

  7. Neutrino Emission Processes in Neutron Star Cores Enhanced emission in inner cores of massive neutron stars Everywhere in neutron star cores

  8. Neutrino Emission Processes in Neutron Star Cores Outer coreInner core Slow emission Fast emission Direct Urca, N/H Pion condensate erg cm-3 s-1 } } Kaon condensation Or quark matter Fast } } STANDARD Modified Urca } NN bremsstrahlung Enhanced emission in inner cores of massive neutron stars: Everywhere in neutron star cores:

  9. FAST AND SLOW NEUTRINO COOLING SUN

  10. SUPERFLUIDITY IN NEUTRON STARS Density dependence of the gap After Lombardo & Schulze (2001) A=Ainsworth, Wambach, Pines (1989) S=Schulze et al. (1996) W=Wambach, Ainsworth, Pines (1993) C86=Chen et al. (1986) C93=Chen et al. (1993) At high densities superfluidity disappears

  11. Effects of superfluidity • Cooper pairing at T<Tc: • Modifies heat capacity • Suppresses ordinary neutrino • processes • Creates a new process: neutrino • emission due to Cooper pairing • Possibly affects heat transport?

  12. SUPERFLUID SUPPRESSION OF NEUTRINO EMISSION A=1S0 B=3P2 (m=0) C=3P2 (m=2)

  13. Cooper pairing neutrino emission Flowers, Ruderman and Sutherland (1976) Only the standard physics involved

  14. Distribution over the stellar core T=3x108 K 2x108 108 6x107 3x107

  15. THREECOOLING STAGES

  16. Analytical estimates Thermal balance of cooling star with isothermal interior Slow cooling via Modified Urca process Fast cooling via Direct Urca process

  17. OBSERVATIONS AND BASIC COOLING CURVE Nonsuperfluid star Nucleon core EOS PAL (1988) Modified Urca neutrino emission: slow cooling 1=Crab 2=PSR J0205+6449 3=PSR J1119-6127 4=RX J0822-43 5=1E 1207-52 6=PSR J1357-6429 7=RX J0007.0+7303 8=Vela 9=PSR B1706-44 10=PSR J0538+2817 11=PSR B2234+61 12=PSR 0656+14 13=Geminga 14=RX J1856.4-3754 15=PSR 1055-52 16=PSR J2043+2740 17=PSR J0720.4-3125

  18. MODIFIED AND DIRECT URCA PROCESSES 1=Crab 2=PSR J0205+6449 3=PSR J1119-6127 4=RX J0822-43 5=1E 1207-52 6=PSR J1357-6429 7=RX J0007.0+7303 8=Vela 9=PSR B1706-44 10=PSR J0538+2817 11=PSR B2234+61 12=PSR 0656+14 13=Geminga 14=RX J1856.4-3754 15=PSR 1055-52 16=PSR J2043+2740 17=PSR J0720.4-3125

  19. BASIC PHENOMENOLOGICAL CONCEPT Neutrino emissivity function Neutrino luminosity function

  20. MODIFIED AND DIRECT URCA PROCESSES: SMOOTH TRANSITION

  21. MODIFIED AND DIRECT URCA PROCESSES: SMOOTH TRANSITION 2p proton SF 9=PSR B1706-44 10=PSR J0538+2817 11=PSR B2234+61 12=PSR 0656+14 13=Geminga 14=RX J1856.4-3754 15=PSR 1055-52 16=PSR J2043+2740 17=PSR J0720.4-3125 1=Crab 2=PSR J0205+6449 3=PSR J1119-6127 4=RX J0822-43 5=1E 1207-52 6=PSR J1357-6429 7=RX J0007.0+7303 8=Vela

  22. MODIFIED AND DIRECT URCA PROCESSES: SMOOTH TRANSITION -- II 2p proton SF Mass ordering is the same!

  23. Neutron stars with strongproton and mild neutron superfluidities in the cores

  24. MAIN PHYSICAL MODELS • Problems: • To discriminate between neutrino mechanisms • To broaden transition from slow to fast neutrino • emission

  25. TESTING THE LEVELS OF SLOW AND FAST NEUTRINO EMISSION Slow neutrino emission: Fast neutrino emission: Two other parameters are totally not constrained

  26. CONNECTION: X-ray transients • Aql X-1 • 4U 1608-522 • RX J1709-2639 • KS 1731-260 • Cen X-4 • SAX J1810.8-2609 • XTE J2123-058 • 1H 1905+000 • SAX 1808.4-3658 Data collected by Kseniya Levenfish Kaon condensate Pion condensate Direct Urca

  27. Broadening of threshold for fast neutrino emission Superfluidity: Suppresses ordinary neutrino processes Initiates Cooper-pairing neutrino emission Should be: Strong in outer core to suppress modified Urca Penetrate into inner core to broaden direct Urca threshold Can be: proton or neutron Nuclear physics effects E.,g.pion polarization Voskresensky &Senatorov (1984, 1986) Schaab et al. (1997) Magnetic broadening Baiko & Yakovlev (1999)

  28. Effects of accreted envelopes and surface magnetic fields

  29. SUMMARY OF CONNECTIONS

  30. CONCLUSIONS Cooling neutron stars Soft X-ray transients Today • Constraints on slow and fast neutrino emission levels • Mass ordering

  31. CONCLUSIONS Ordinary cooling isolates neutron stars of age 1 kyr—1 Myr • There is one basic phenomenological cooling concept • (but many physical realizations) • Main cooling regulator: neutrino luminosity function • Warmest observed stars are low-massive; their neutrino luminosity • seems to be <= 1/30 of modified Urca • Coldest observed stars are more massive; their neutrino luminosity • should be > 30 of modified Urca (any enhanced neutrino emission would do) • Neutron star masses at which neutrino cooling is enhanced are not constrained • The real physical model of neutron star interior is not selected Connections • Directly related to neutron stars in soft X-ray transients (assuming deep crustal • heating). From transient data the neutrino luminosity of massive stars • is enhanced by direct Urca or pion condensation • Related to magnetars and superbusrts Future • New observations and accurate theories of dense matter • Individual sources and statistical analysis

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