The Cluster-Type Variable VZ CANCRI.
Abstract
Between December, 1950, and April, 1954, 1449 photoelectric observations of the short-period variable VZ Cancri = HD 73857 were obtained. The star has been classified by Whitney (1950) and by Joy and Wilson (1950) as a cluster-type variable. From observations on 47 ascending branches the star is found to have a beat period of 0d.716292 I 0d.000005 m.e., with a primary period of 7836376 I 0 01 m.e. The moment of occurrence of median magnitude on the ascending branch, r = 0.5 ( + m ) may be well represented by = Hel. J.D. 2433631.84615 + od.17836376E + Od.00193 sin (m) +5 +1 +5 - od.()()37t COS + 4m.e. where `k(m) is the beat phase at T(m) and E is the primary cycle number. No other period appears to be present. An inspection of the published periods for the twelve cluster-type stars with known secondary periods shows that the stars fall into two distinct groups corresponding to the period break at about 0d.25 found by Kukarkin and Parenago (1937) and S. Gaposchkin (1938) from analyses of light-curves and frequencies of period occurrence. The ratios of secondary to primary period for stars with Po less than 0d.20 and P0 greater than 0d.35 are quite different. The effect is tentatively ascribed to a difference in the depth of the hydrogen convection zone in the two groups of stars.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1955
- DOI:
- 10.1086/146035
- Bibcode:
- 1955ApJ...121..690F