What are high l modes, if anything?

  • J. E. Hestand
Degenerate and Pre-Degenerate Variables
Part of the Lecture Notes in Physics book series (LNP, volume 274)


Theoretical analyses of the pulsational instability of compact objects indicate that pulsation modes of high spherical harmonic index,l, are expected to be unstable. The amplitudes of the observed, presumably low l,modes with 1>3 will bring them below the observable threshold for ground based photometry. We point out, however, that observations with a space telescope should reveal the presence of modes of 1 4-5 simply because the absence of scintillation noise does not limit the amplitude sensitivity. We also point out that rotational splitting has been identified in a large number of the compact pulsators; in principle, this generates a set of (21+1) modes for each k and l, and we show that the beating together of these modes may have observable consequences. We examine the prospects for observing the beating of the pulsation modes with high spherical harmonic index,l. We show that in some cases this beating may result in something which would look essentially like a flare. We discuss the prospects for observing this effect, and the very real possibility that it has already been observed.


Light Curve Rotation Period Beat Frequency Mode Beating Rotational Splitting 


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Copyright information

© Springer-Verlag Berlin Heidelberg 1987

Authors and Affiliations

  • J. E. Hestand
    • 1
  1. 1.Department of AstronomyUniversity of TexasAustin

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