The unusual classical Cepheid HR 7308: 1966–1969

Abstract

The small-amplitude classical cepheid HR 7308 has the shortest period known in our Galaxy for a classical cepheid. 1966–1969 photoelectric observations together with more recent data show a period of 1$\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{d}$49078 with sinusoidal light variations. Except for the presence of the beat period, no secondary period can be found in the extensive 1966 data. The lack of a secondary period near p₁/p₀ = 0.7 sets HR 7308 apart from many other short-period classical cepheids.

The amplitude of HR 7308 varies an a timescale near 970 days. The variations may be periodic. The available data do not at present allow us to distinguish between the Blazhko Effect (modulation of a regular variation) and a model with two very close interfering periods in HR 7308.