Chromospheric activity in H and K lines of Arcturus on 1984 February 14

Abstract

We have obtained a large amount of high-dispersion spectra of Arcturus using our coude spectrograph attached to our 1-metre telescope. From this collection, we picked out an unbroken sequence of 5 spectra of the CaII H and K lines taken in a period of 4 hours on 1984 February 14. Their analysis shows that we were possibly witnessing a chromospheric eruption on the star. The following sequence was seen: the line profile became asymmetrical — the asymmetry remained while the peak emission increased — the profile became symmetrical once again. The largest asymmetry was 20% between the red and violet components of K 2, and the maximum peak emission was some 20% above normal. There were also changes in K 1. At the peak emission of K 2 emission core appeared in the self-absorbed centre of K 3.