Other
Scientific paper
Sep 1986
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1986phdt.........4y&link_type=abstract
Thesis (PH.D.)--THE UNIVERSITY OF BRITISH COLUMBIA (CANADA), 1986.Source: Dissertation Abstracts International, Volume: 48-09,
Other
Scientific paper
In conventional radial-velocity techniques, wavelength calibration in stellar spectra is limited by collimation and guiding errors. These errors can be largely eliminated by imposing absorption lines of known wavelengths on the spectra. The most suitable natural absorption lines belong to the R-branch (3-0) vibration-rotation band of HF. The calibration is achieved by placing an absorption cell filled with HF gas into the stellar beam. The small-amplitude delta Scuti stars typically have a velocity-light amplitude ratio 2K/Deltam_{rm v} of about 92kms^{-1 }mag^{-1}. Therefore, a velocity precision of just +/-0.1kms ^{-1} would already be equivalent to a precision of about +/-0.001 ^{rm m} in the light curve. The HF precision radial-velocity technique also enables the examination of individual spectral line for profile variations. The star 20 CVn is a 0.122^{ rm d} delta Del -type delta Scuti variable. A 2K value of 1.4kms^{-1} was measured for the Ca II lambda8662 line. This gives a 2K/Deltam _{rm v} value of about 40kms ^{-1}{rm mag}^ {-1} and could imply nonradial pulsation. The star rho Pup is a 0.141 ^{rm d} delta Del-type delta Scuti variable. The line intensities of the stellar lines have been found to vary in phase with the light curve. The amplitude of these variations are between 0.5% and 1% of the continuum. The variations can be considered as spectral -type variations caused by the variations of the effective temperature of the star over the pulsation cycle. The star o^1 Eri is a 0.082 ^{rm d} broad-line delta Scuti variable. The Ca II lambda8662 line has a 2K amplitude of 4.3kms^{-1}. Line -profile variations, with an amplitude of about 2% of the continuum, have been observed in the Ca II line. The variations can be characterised as the temporal movement of "features" across the broadened line profile. This would suggest the existence of nonradial pulsation in the star. The star beta Cas is a 0.104 ^{rm d} broad-line delta Scuti variable. The Ca II lambda8662 line has a 2K value of about 7kms^{-1}. The H I velocity curve has been found to lag the other velocity curves by about 2% in phase. Line-profile variations, with an amplitude of about 1% of the continuum, have been observed in the Ca II line. The variations can be characterised as phase-dependent linewidth variations.
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