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Thermal emission areas of heated neutron star polar caps

  • M. RudermanEmail author
  • A. M. Beloborodov
Conference paper

Abstract

Observed hot spots on neutron stars are often associated with polar caps heated by the backflow of energetic electrons or positrons from accelerators on bundles of open magnetic field lines. Three effects are discussed that may be relevant to formation of hot spots and their areas. (1) The area of a polar cap is proportional to the ratio of the star’s surface dipole field to the local field at the polar cap. Because the field is coupled to the evolving spin of the superfluid core of the star, this ratio can depend on the stellar spin and its history. (2) The hot emission area may appear smaller to a distant observer when emitted X-rays propagate through electron-positron plasma created in the magnetosphere. The X-rays then change their energy spectrum because of cyclotron resonant scattering by pairs. (3) Hot spots may form on the star’s surface as a result of crust motions that are driven by the pull of core flux tubes pinned to the crust. Such motions twist the footprints of closed magnetic loops of the magnetosphere and induce an electric current in the loop, which will heat those footprints.

Keywords

Neutron stars Polar caps Magnetic fields 

PACS

97.60.Jd 

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References

  1. [Beloborodov and Thompson, 2007]
    Beloborodov, A.M., Thompson, C.: Astrophys. J. 657, 967 (2007) ADSCrossRefGoogle Scholar
  2. [Caraveo et al., 2004]
    Caraveo, P.A., et al.: Science 305, 376 (2004) ADSCrossRefGoogle Scholar
  3. [Jones, 2004]
    Jones, P.: Phys. Rev. Lett. 93, 271101 (2004) Google Scholar
  4. [Pavlov et al., 2001]
    Pavlov, G.G., et al.: Astrophys. J. 552, L129 (2001) ADSCrossRefGoogle Scholar
  5. [Pavlov et al., 2004]
    Pavlov, G.G., Sanwal, D., Teter, M.: In: Camilo, F., Gaensler, B. (eds.) Young Neutron Stars and Their Environments, IAU Symposium 218, p. 239. ASP, San Francisco (2004) Google Scholar
  6. [Ruderman, 2005]
    Ruderman, M.: Causes and consequences of magnetic field changes in neutron stars. astro-ph/0510623 (2005) Google Scholar
  7. [Yakovlev et al., 2002]
    Yakovlev, D.G., et al.: In: Becker, W., Lesch, H., Trümper, J. (eds.) Proceedings of the 270 WE-Heraeus Seminar on Neutron Stars, Pulsars and Supernova Remnants, p. 287. Max-Plank-Institut für extraterrestrische Physik, Garching bei München (2002) Google Scholar
  8. [Zavlin and Pavlov, 2004]
    Zavlin, V.E., Pavlov, G.G.: Mem. Soc. Astron. Ital. 75, 458 (2004) ADSGoogle Scholar

Copyright information

© Springer 2007

Authors and Affiliations

  1. 1.Physics Department and Columbia Astrophysics LaboratoryColumbia UniversityNew YorkUSA

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