Activity in late-type stars. IV. The 1980 August 20 flare on proxima Centauri revisited.

Abstract

This paper presents a reanalysis of simultaneous ultraviolet and soft X-ray observations of a flare on the dMe star, Proxima Centauri. Using an emission measure analysis, as well as density sensitive line ratios, the electron density and the total emitting volume of the flare plasma which is at midtransition region temperatures are derived. These, and the corresponding parameters derived from the previously published X-ray light curve, are compared in the framework of a simple loop model of the flare. This analysis suggests that the coronal X-rays and the transition-region UV line emission arose in volumes of comparable extent. The combined L-alpha and total transition region line losses are found to be comparable to the estimated total coronal losses during the flare. This latter conclusion disagrees with the original deduction of Haisch et al. (1983) that the transition region losses are unimportant compared with the coronal losses.