BV photometry and H-alpha spectroscopy of the RS Canum Venaticorum binary V711 Tauri

Abstract

Differential BV photometry of V711 Tau obtained on a total of 120 nights during the years 1984-1991 and H-alpha spectroscopy obtained on 14 nights during the 1990-1991 observing season are presented. We find that the mean light level of the system during the period 1975-1982 was fainter by about 0.05 mag than that during the period 1982-1991. The change in the mean light level probably arises from a global reduction in the area of spots or from the disappearance of spots from the polar region. At larger amplitudes the brightness at minimum decreases and the brightness at maximum increases, both converging to a particular value of Delta(V) at very low amplitudes. Phase of light minima observed during 1975-1991 lie on two independent near-straight lines, implying that spots are confined predominantly to two different latitude belts. The H-alpha equivalent widths did not show any orbital modulation during the period of our observations. The spectra obtained on one night (February 6, 1991) show a sudden drop in equivalent width; this occurs during the descending branch of the light curve.