CAOSP abstracts, Volume: 27, No.: 3, year: 1998
- Author(s): KURTZ, D.W.
- Journal: Contributions of the Astronomical Observatory Skalnate Pleso,
vol. 27, no. 3, p. 264-271.
- Date: 04/1998
- Title: Some recent results for the roAp stars
- Keyword(s): STARS: CHEMICALLY PECULIAR, STARS: OSCILLATING
- Pages: 264 -- 271
Three topics are discussed: 1) Photometric observations of the rapidly
oscillating Ap stars have shown that the pulsation amplitude drops
dramatically as a function of wavelength from the blue to the red.
A theoretical derivation, plus modelling, indicates that this is because
the vertical wavelength of the pulsation mode is short compared to the scale
height of the atmosphere; in fact, it indicates that we are seeing a pulsation
node in the observable atmosphere. Radial velocity observations, and
theoretical calculations now support this. The implication for other research
on CP stars is that this can provide observational constraints on the
atmospheric structure independent of traditional spectral analysis.
2) Luminosities of roAp stars can be determined from asteroseismology.
A recent comparison of such asteroseismic luminosities with HIPPARCOS
luminosities is shown. This suggests that roAp stars have lower temperatures
and/or smaller radii than previous models have used, or that the magnetic
fields in these stars alter the frequency separations. 3) The latest results
of our long-term monitoring of the pulsation frequencies in certain roAp
stars are discussed. There is a clear cyclic variability to the pulsation
cavity, hence the sound speed and/or sound travel time (radius) of these stars.
This might be indicative of magnetic cycles at a level that magnetic
measurements cannot currently detect, although there is no theoretical
support for such an idea.
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