A Discussion on solar studies with special reference to space observations - OAO observations of magnesium II emission in late-type stars

Abstract

The presence of Ca II H and K emission and λ = 1083 nm of He I in late-type stars suggests that the outer atmospheres of these stars bear some resemblance to the solar atmosphere. Dr Zirin has discussed the appearance of these features in a number of stars in the preceding paper. Because spectral features in cool stars are most sensitive to temperature differences in the ultraviolet, observations of ultraviolet spectra should yield considerable information concerning the nature of chromospheric structure in stars. Over the past year the Orbiting Astronomical Observatory OAO-2 has scanned a number of bright stars of spectral type G and later in the region 180 to 370 nm with a resolution of about 2.5 nm. I will discuss some of the characteristics of these low-resolution spectra with particular emphasis on the appearance of the λ = 280 nm doublet of Mg II.