1. COOLING OF YOUNG NEUTRON STARS AND THE SUPERNOVA 1987A D.G. Yakovlev Ioffe Physical Technical Institute, St.-Petersburg, Russia Ladek Zdroj, February 2008, 1.Introduction: Is there a problem? 2.Neutron star structure and cooling 3.Thermal relaxation 4.Summary

2. INTRODUCTION: IS THERE A PROBLEM? Burrows et al. ApJ 543, L149 (2000): High-resolution Chandra observations Park et al. ApJ 610, 275 (2004): Discovery: Shelton, Feb. 23-24, 1987 Las Campanes, Chile

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

4. Nonsuperfluid star Murca neutrino emission: slow cooling THE BASIC COOLING CURVE

5. NEUTRINO EMISSIVITY AND THERMAL CONDUCTIVITY THROUGHOUT A NEUTRON STAR Negel & Vautherin (1973)

6. HEAT CAPACITY THROUGHOUT A NEUTRON STAR

7. Prakash, Ainsworth, Lattimer (1988) Page, Applegate (1992) EOS npe-matter

8. WILL DIRECT URCA HELP? Nonsuperfluid neutron star models

9. INITIAL THERMAL RELAXATION: LOOK FROM INSIDE AND OUTSIDE Gnedin et al. (2001)

10. A LOOK FROM INSIDE: FAST COOLING OF A NONSUPERFLUID STAR

11. A LOOK FROM INSIDE: SLOW COOLING OF A NONSUPERFLUID STAR

12. THE RELAXATION TIME t W =? Nomoto, Tsuruta, ApJ 312, 711 (1987) Lattimer, Van Riper, Prakash, Prakash, ApJ 425, 802 (1994) Gnedin, Yakovlev, Potekhin MNRAS 325, 725 (2001)

13. SCALING OF THE RELAXATION TIME Lattimer et al. (1994) t 1 = independent of neutron star model!

14. RELAXATION TIME OF A NONSUPERFLUID STAR Physics of crustt W (years) Real51 No crust neutrinos260 Plasmon decay neutrinos in crust 68 No neutron heat capacity in crust 15 Thermal conductivity for point-like nuclei 130 Isothermal interior0 Other physics: Crust-core boundary Thermal conductivity in the core

15. A LOOK FROM INSIDE OF SUPERFLUID STARS

16. RELAXATION TIME OF A SUPERFLUID STAR Crust physicst W (years) Non-superfluid crust51 Weak neutron superfluidity 20 Strong neutron superfluidity 15

17. Page, Geppert, Weber (2006) VERY SHORT RELAXATION Neutron star with very high thermal conductivity in the inner crust Nonsuperfluid strange stars

18. CONCLUSIONS Cooling of young neutron stars is almost insensitive to the physics of their cores; young stars are excellent natural laboratories of inner crust A hypothetical neutron star in SN87A should be sufficiently cold To explain this one should shorten the thermal relaxation time The relaxation is mainly determined by the physics of the crust (much less sensitive to the physics of the core) The natural way to shorten the relaxation time is to assume strong neutron superfluidity in the inner crust Other ways to shorten the relaxation are also possible New observations would be crucial

19. J.M. Lattimer, K.A. Van Riper, M. Prakash, M. Prakash, Rapid cooling and the structure of neutron stars, Astrophys. J., 425, 802, 1994. O.Y. Gnedin, D.G. Yakovlev, A.Y. Potekhin, Thermal relaxation in young neutron stars. Mon. Not. Roy. Astron. Soc. 324, 725, 2001. REFERENCES