Shusaku Kawabata

Spectroscopic observations of Zeta Aurigae during the 1971-72 eclipse. II. Intensity of the chromospheric K-line and radial velocities of chromospheric lines

The chromospheric phases in the 1971–72 eclipse were observed at wavelength regions containing the K-line of ionized calcium on six nights at ingress and on eight nights at egress at the Okayama Astrophysical Observatory. The linear dispersion of the spectrograms is about 10 Å mm−1. The spectrograms were measured for line intensities of the K-line and for radial velocities of metallic and hydrogen lines.The results are compared with those obtained in the earlier eclipses. The intensities of the chromospheric K-line during this eclipse were relatively ‘weak’ at both ingress and egress and were similar to those in the 1939–40 eclipse. It seems that the chromospheric activity of ζ Aurigae increased after 1939, reached a maximum at 1950–56, and then decreased again until 1971. The radial velocities of the chromospheric lines of hydrogen atoms, ionized calcium, and some other atoms and ions varied with phase showing almost the same characteristic features as in most earlier eclipses. Intensities and velocities were also measured for satellite lines of the K-line.

Circumstellar line of Cai λ6572 in Zeta Aurigae and 31 Cygni

In the 1974 eclipse of Zeta Aurigae the satellite line of the Cai intercombination line at 6572 Å appeared in all the phases observed, i.e., near the mid-eclipse and egress, although its equivalent width, ∼100–200 mÅ, and velocity deviation, ∼−20 im s−1, from the principal line were considerably less than those for the satellite line found just after the fourth contact of the 1971–72 eclipse. 31 Cygni also showed a similar satellite line to Zeta Aurigaes in the 1974 eclipse, not only in the 1972 eclipse but also outside the eclipse. These satellite lines should be due to the circumstellar gas expanding from the binary systems.