Lyman-alpha emission from low dispersion IUE spectra

Abstract

In spite of its importance as cooling mechanism of the chromosphere of late type stars, the hydrogen Lyman-alpha line has been neglected in most IUE programmes The high geocoronal background and the saturation often seen in the stellar emission peak are the major problems that prevent accurate determination of the Lyman alpha flux.

We have developed a technique that allows us to overcome both of these problems by fitting an ellipsoidal surface to the geocoronal background and gaussian profiles to the stellar signal. Results on a limited sample of stars are presented.