Astron. Astrophys. 346, 465-480 (1999)

Impact of internal heating on the thermal evolution of neutron stars

Ch. Schaab ¹, A. Sedrakian ², F. Weber ^1,3 and M.K. Weigel <sup>4

1</sup> Institut für theoretische Physik, Ludwig-Maximilians Universität, Theresienstrasse 37, D-80333 München, Germany
² Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14853, USA
³ Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
⁴ Sektion Physik, Ludwig-Maximilians Universität, Am Coulombwall 1, D-85748 Garching, Germany

Received 26 October 1998 / Accepted 4 March 1999

Abstract

The impact of various competing heating processes on the thermal evolution of neutron stars is investigated. We show that internal heating leads to significantly enhanced surface temperatures for pulsars of middle and old age. The heating due to thermal creep of pinned vortices and due to outward motion of proton vortices in the interior of the star leads to a better agreement with the observed data in the case of enhanced cooling. The strong pinning models are ruled out by a comparison with the cooling data on the old pulsars. For millisecond pulsars, the heating due to thermal creep of pinned vortices and chemical heating of the core have the largest impact on the surface temperatures. The angular dependence of the heating rates require two dimensional cooling simulations in general. Such a simulation is performed for a selected case in order to check the applicability of one-dimensional codes used in the past.

Key words: stars: neutron stars: evolution

Present address: Kernfysisch Versneller Instituut, Zernikelaan 25, 9747 AA Groningen, The Netherlands

Send offprint requests to: Ch. Schaab (schaab@gsm.sue.physik.uni-muenchen.de)

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Contents

• 1. Introduction
• 2. Thermal and rotational evolutions
  • 2.1. Equations of thermal evolution
  • 2.2. The normal component
  • 2.3. The superfluid component
• 3. Dissipative motion of vortex lattices
  • 3.1. Vortex pinning at nuclei
  • 3.2. Corotating regime in the crust
  • 3.3. Electron-vortex scattering in superfluid core
  • 3.4. Decay of vortices
• 4. Readjustment to equilibrium structure
  • 4.1. Crust cracking
  • 4.2. Chemical heating
• 5. Additional ingredients and comparison of the efficiency of the heating mechanisms
  • 5.1. Equation of state
  • 5.2. Neutrino emissivity
  • 5.3. Superfluidity
  • 5.4. Photosphere
  • 5.5. Comparison of the efficiency of the heating mechanism
• 6. Observed data
• 7. Results and discussion
  • 7.1. Standard cooling
  • 7.2. Enhanced cooling
  • 7.3. Accretion
  • 7.4. Millisecond pulsars
  • 7.5. Two dimensional simulations
• 8. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1999

Online publication: May 21, 1999
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