Observation of Quasi-Continuum Line Emission from F[CLC]e[/CLC] [CSC]vii[/CSC] to F[CLC]e[/CLC] [CSC]x[/CSC] in the Extreme-Ultraviolet Region below 140 Å

Abstract

The line emission of Fe VII-Fe X ions in the extreme-ultraviolet region below 140 Å was measured in controlled laboratory experiments under conditions representative of stellar coronae. The observations are compared with predictions from standard spectral models using the CHIANTI and MEKAL atomic databases. We find that the atomic databases miss most of the line flux in this region. While some of the missing lines form isolated features, most add up to form a quasi continuum in the 60-120 A region. This incompleteness can explain the poor fit when applying global-fitting techniques to spectra from cool stars measured by the Extreme-Ultraviolet Explorer satellite, the origin of which has been a source of controversy since the original observations were made.