Other
Scientific paper
Apr 1981
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1981mnras.195...31a&link_type=abstract
Monthly Notices of the Royal Astronomical Society, vol. 195, Apr. 1981, p. 31-34. Research supported by the Scientific and Tech
Other
2
Semiregular Variable Stars, Stellar Motions, Stellar Spectra, Absorption Spectra, Emission Spectra, Mira Variables, Radial Velocity
Scientific paper
Optical velocities of semi-regular (SR) and irregular (Lb) variables are analyzed for a K-term. There is evidence for a dependence upon stellar period. Absorption lines in shorter period non-emission SR variables are blue-shifted relative to the centre-of-mass velocity by about 6 + or - 3 km/s. Emission-line SR variables give a non-negative absorption K-term and Lb variables give no K-terms other than zero. Comparison is made with the K-terms implied by the OH velocity pattern in long-period variables. Dispersion ratios are also calculated. They are 0.69 + or - 0.16 for non-emission, and 0.74 + or - 0.20 for emission variables (from absorption lines). Kinematics suggest that the sequence Lb-SR(non-emission)-SR(emission)-Mira is a sequence of increasing age. It is suggested that this sequence may also be the sequence indicating the direction of evolution.
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