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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