Photometric variations of Orion population stars. IV - Coordinated spectroscopy in 1984/1985 with some success for RY Tau
Abstract
UBVRI and Hα photometry and image-tube-scanner spectra have been obtained for six T Tauri stars during the 1984/1985 Milky Way season. With the addition of simultaneous spectra and photometry obtained in 1979 by G. Herbig, the authors have data on RY Tau spanning a range of 1.6 mag in V. The spectra confirm that the EW (Hα) increases as the star fades and show that Hβ behaves similarly. The flux in the Hα line generally decreases as the star fades, but can change independently of V by factors of 3 or more on time scales af a week or less. U-B and B-V are essentially independent of V and (R-I) steadily reddens as the star fades. (V-R) shows a turnaround. It is argued from these data that the seat of the variability in RY Tau is primarily the photosphere and that changes in the fractional areas covered by hotter and cooler components account for the observed color and spectral changes. Dramatic changes in Hα were seen in two stars - CO Ori, which developed a P Cygni profile, and VY Tau, which increased its EW (Hα) by a factor of 10.