Light curves from rapidly rotating neutron stars

Kazutoshi Numata, Umin Lee

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


We calculate light curves produced by a hotspot of a rapidly rotating neutron star, assuming that the spot is perturbed by a core r mode, which is destabilized by emitting gravitational waves. To calculate light curves, we take account of relativistic effects, such as the Doppler boost due to the rapid rotation and light bending, assuming the Schwarzschild metric around the neutron star. We assume that the core r modes penetrate to the surface fluid ocean to have sufficiently large amplitudes to disturb the spot. For an l'=m core r mode, the oscillation frequency ω≈ 2mΩ/[l' (l'+ 1)] defined in the corotating frame of the star will be detected by a distant observer, where l' and m are, respectively, the spherical harmonic degree and the azimuthal wavenumber of the mode, and Ω is the spin frequency of the star. In a linear theory of oscillation, using a parameter A, we parametrize the mode amplitudes, such that max (|ξθ|, |ξφ|)/R=A at the surface, where ξθ and ξφ are, respectively, the θ and φ components of the displacement vector of the mode and R is the radius of the star. For the l'=m= 2 r mode with ω= 2Ω/3, we find that the fractional Fourier amplitudes at ω= 2Ω/3 in light curves depend on the angular distance θs of the spot centre measured from the rotation axis and become comparable to or even larger than A 0.001 for small values of θs.

Original languageEnglish
Pages (from-to)481-490
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Publication statusPublished - 2010 Dec


  • Stars: magnetic field
  • Stars: neutron
  • Stars: oscillations
  • Stars: rotation

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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