COOLING OF YOUNG NCOOLING OF YOUNG NEUTRON STEUTRON STAARRSSAND THE SUPERNOVA 1987AAND 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 cooling3. Thermal relaxation4. Summary

INTRODUCTION: IS THERE A PROBLEM?

Burrows et al. ApJ 543, L149 (2000):High-resolution Chandra observations

2 44 ( )

13 km sL R T

R

34(0.5 2 keV) 2.3 10 erg/sXL

62 10 KsT

Park et al.ApJ 610, 275 (2004):

34(2 10 keV) 1.5 10 erg/sXL

Discovery: Shelton, Feb. 23-24, 1987Las Campanes, Chile

Stage Duration Physics

Relaxation 10—100 yr Crust

Neutrino 10-100 kyr Core, surface

Photon infinite Surface, core,

reheating

THREE COOLING STAGES

Nonsuperfluid starMurca 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 COOLINGOF A NONSUPERFLUID STAR

A LOOK FROM INSIDE: SLOW COOLINGOF A NONSUPERFLUID STAR

THE RELAXATION TIME

tW=?

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

2

1 3/ 2

1

1 km (1 / )Wg

Rt t

r R

Lattimer et al. (1994)

t1 = independent of neutron star model!

ccR R R

2 / = thermal diffusion

time scale through a slab of

width

W Vt C l

l

1 28 years for a standard

nonsuperfluid star

t

RELAXATION TIME OF A NONSUPERFLUID STAR

Physics of crust tW (years)

Real 51

No crust neutrinos 260

Plasmon decay neutrinos in crust

68

No neutron heat capacity in crust

15

Thermal conductivity for point-like nuclei

130

Isothermal interior 0

Other physics: Crust-core boundaryThermal conductivity in the core

A LOOK FROM INSIDE OF SUPERFLUID STARS

RELAXATION TIME OF A SUPERFLUID STAR

Crust physics tW (years)

Non-superfluid crust 51

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, 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