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

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 , 1987 Las Campanes, Chile

StageDurationPhysics Relaxation10—100 yrCrust Neutrino kyrCore, surface PhotoninfiniteSurface, core, reheating THREE COOLING STAGES

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

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

HEAT CAPACITY THROUGHOUT A NEUTRON STAR

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

WILL DIRECT URCA HELP? Nonsuperfluid neutron star models

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

A LOOK FROM INSIDE: FAST COOLING OF A NONSUPERFLUID STAR

A LOOK FROM INSIDE: SLOW COOLING OF A NONSUPERFLUID STAR

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)

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

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

A LOOK FROM INSIDE OF SUPERFLUID STARS

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

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

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

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