Magnesium emission variability among late-type giant stars

Abstract

We have investigated the variability of the emission cores in the h and k Unes of Mg n in a sample of 21 late-type giants. We have used high resolution line profiles obtained by IUE \o determine not only the total emission intensity, but also the ratio of the intensities of the shortward and longward components of the doubly-reversed emission. We argue that variations in the total emission intensity are indicative of variations in chromospheric heating, while variations in the ratio can be interpreted in terms of variations in structures in the corona and outer atmosphere.

Mass Loss on the Red Giant Branch: Plasmoid-driven Winds above the RGB Bump

“…Such phenomena are expected to lead to measurable variability in the winds. Evidence for variability in mass loss from cool giants was indeed reported in the profiles of the emission cores of the MgII h and k lines (Mullan & Stencel 1982).…”

Chromospheric and Coronal Indicators of Stellar Magnetic Structure

“…For the sources of F x 9 AF"^ data: see Schrijver et al (1982). The solar data are from Varana and Rosner (1978 : Ayres* Marstad and Linsky (1981); Ayres et al '(1982); de Castro et al (1981);Hartmann* Dupree and Raymond (1982); Linsky et al (1982); Mullan and Stencel (1982); Oranje (1982b); Oranje*Zwaan and Middelkoop (1982) ;Simon* Linsky and Stencel (1982 Bopp and Stencel (1981) T Tau stars: Cram et al (1980); Tjin A Die (1982) Herbig Ae star: Tjin A Die et al (1982) Fig. 4b: Small open symbols: data points from Fig.…”