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

2. Cooling Theory: Primitive and complicated at once

3. Basic Ideas

4. PRE-PULSAR HISTORY Stabler (1960) – PhD, First estimates of X-ray surface thermal emission Chiu (1964) – Estimates that neutron stars can be discovered from observations of thermal X-rays Morton (1964), Chiu & Salpeter (1964), Bahcall & Wolf (1965) – First simplified cooling calculations Tsuruta & Cameron (1966) – Basic formulation of all elements of the cooling theory

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

6. StageDurationPhysics Relaxation10—100 yrCrust Neutrino10-100 kyrCore, surface PhotoninfiniteSurface, core, reheating THREE COOLING STAGES

7. INITIAL THERMAL RELAXATION: LOOK FROM INSIDE AND OUTSIDE

8. 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 Talks by Frank Haberl and Slava Zavlin

9. 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

10. BASIC PHENOMENOLOGICAL CONCEPT Neutrino emissivity functionNeutrino luminosity function Problems: To discriminate between neutrino mechanisms To broaden transition from slow to fast neutrino emission

11. MODIFIED AND DIRECT URCA PROCESSES: SMOOTH TRANSITION

12. MODIFIED AND DIRECT URCA PROCESSES: SMOOTH TRANSITION 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 2p proton SF

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

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

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

16. 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 E.,g. pion polarization Voskresensky &Senatorov (1984, 1986) Schaab et al. (1997) Magnetic broadening Baiko & Yakovlev (1999) Nuclear physics effects

17. Effects of accreted envelopes and surface magnetic fields

18. Summary of cooling regulators Regulators of 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.

19. Direct Urca Pion condensate Kaon condensate 1Aql X-1 24U 1608-522 3RX J1709-2639 4KS 1731-260 5Cen X-4 6SAX J1810.8-2609 7XTE J2123-058 81H 1905+000 9SAX 1808.4-3658 Data collected by Kseniya Levenfish CONNECTION: X-ray transients Talk by Rudy Wijnands

20. CONNECTION: Magnetars Kaminker et al. (2006)

21. SUMMARY OF CONNECTIONS ObjectsPhysics which is tested Middle-aged isolated NSaNeutrino luminosity function Composition and B-field in heat-blanketing envelopes Young isolated NSsCrust Quasistationary XRTsNeutrino luminosity function Composition and B-field in heat-blanketing envelopes Deep crustal heating Quasipersistent XRTs KS 1731—260; MXB 1659—29 Crust Deep crustal heating SuperburstsCrust Magnetars after outburstsCrust Magnetars in quasistationary states ??

22. CONCLUSIONS Future Today New observations and good practical theories of dense matter Individual sources and statistical analysis Cooling neutron starsSoft X-ray transients Constraints on slow and fast neutrino emission levels Mass ordering

23. 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

24. CONCLUSIONS The case is not solved Plenty of work ahead

25. Enhanced emission in inner cores of massive neutron stars Everywhere in neutron star cores Neutrino Emission Processes in Neutron Star Cores ModelProcess N/H direct Urca Pion condensate Kaon condensate Quark matter Modified Urca Bremsstrahlung

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

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

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

29. Gamow and Shoenberg: Casino da Urca in Rio de Janeiro Neutrino theory of stellar collapse, Phys. Rev. 59, 539, 1941: Unrecordable cooling agent Photo and Story by R. Ruffini Welcome to the Urca World - I

30. Welcome to the Urca World - II