On possible quasi-periodic diameter variations of the carbon star Y Tau

Abstract

An analysis of the available results of direct angular diameter measurements of the carbon star Y Tau in different spectral bands of the optical and near-IR spectral ranges is carried out. It is shown that the available data allow to suggest the presence of periodic or quasi-periodic pulsations of the star with a period close to the possible period of its photometric variability in the corresponding time interval of observations. If the pulsations really take place, then their nature may be such that the star’s luminosity increases with decreasing diameter. At the same time, another interpretation of themeasurement results is possible, where the values of the star’s angular diameter d obtained from the observations in the red part of the optical spectral range correspond to the star’s photosphere, whereas the values d obtained from observations in the near-IR range correspond to the optically thick radiating layers of its extended atmosphere or envelope.