The Delta Scuti star 20 canum venaticorum.
Date
1970
Authors
Penfold, Jack
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Abstract
The Cassegrain spectrograph attached to the 72-inch reflecting telescope at the Dominion Astrophysical Observatory, Victoria was used to obtain spectra of the Delta Scuti star 20 CVn (HD 115604). Altogether 230 spectra were taken on five nights using the 21121 camera of the spectrograph.
Only 216 spectra, representing four night's observations were measured for radial velocity on the B. G. & Z. (Brower, Grant and Zeiss) Oscilloscope Measuring machine at the Observatory. The same twelve stellar lines were measured on all the spectra. Results obtained indicated a variable radial velocity with an amplitude of approximately 2km/sec. A statistical analysis of the result confirmed this variability.
Thirty-two spectra of the non-variable star 30 LMi (HD 90277) were also taken for comparison purposes. This star was chosen as bein as similar in properties as possible to 20 CVn. These spectra were taken and measured under the same conditions as those of 20 CVn. The results were treated in the same way, and then compared with those obtained for 20 CVn. No variation was detected in the case of 30 LMi.
An attempt to determine the period of 20 CVn using the radial velocity observations resulted in two estimates of the period, one = 0ᵈ.135 and another in the vicinity of 0ᵈ.176. The former value appears to fit the data slightly better, and is suggested here as the true period.
Simultaneous photometric and spectroscopic observations were taken on one night in an attempt to determine the phase relationship between the light and velocity curves of 20 CVn. Maximum light apparently occurs somewhere on the rising brach of the velocity curve. This places this star in the same class as the Delta Scuti stars δ Delphini and ρ Puppis.