K emission line widths in the sun and the stars

Abstract

K-emission line widths measured with a micrometer on integrated spectra of the sun have a mean value of 38.2 km/s. A definition is proposed whereby the width is a measure in km/s at the inverse-e value of the difference between the intensity of the brighter K2 peak over the K1 background, reckoned from this latter level. Averaged spectra over different parts of the solar disk show the very appreciable contribution by rotation to the emission line width, making it imperative for any calibration of width with absolute magnitude to use a solar value derived from an integrated spectrum. Arguments are presented showing that the K-emission profile observed in other stars is the profile of the typical bright mottle that should enable the derivation of chromospheric parameters. From measures of Doppler displacements of both K2 and K3, 'dark condensations' as seen on the sun play a role in the atmospheres of stars with K emission.