The ultraviolet variations of the δ Scuti stars 44 Tauri and 71 Tauri.

Abstract

We report on low resolution phase resolved ultraviolet spectrophotometry of the δ Scuti stars, 44 Tau (F2 IV-V) and 71 Tau (F0V) at different phases of their pulsation cycles performed with the International Ultraviolet Explorer. For 44 Tau, the amplitude of the flux variations increases towards shorter wavelengths from about 13% around 3000A, to 40% around 1800A, and the ultraviolet flux varies in phase with the optical brightness as recorded with the Fine Error Sensor (FES). During our observations, 71 Tau exhibited only marginal variations in the ultraviolet. A comparison of the far ultraviolet spectra of 44 Tau at maximum and minimum ultraviolet light with low resolution spectra of constant stars indicates that the effective temperature does not vary by more than 250K over a cycle. The amplitude of the ultraviolet variations seem to scale those in the V band and the behaviour of 44 Tau in the ultraviolet is similar to that of δ Scuti described in Monier (1991).