An extended correlation between the Balmer and soft X-ray emission from solar and stellar flares.

Abstract

The integrated soft X-ray (8-12 Å) fluxes for solar flares, given by Thomas & Teske (1971), have been scaled to the equivalent EXOSAT (0.04-2.0 keV) fluxes using spectra obtained from a variety of rocket-based experiments and a model by Mewe for a 1.5 keV plasma. The data show good agreement with the soft X-ray-Hγ correlation established earlier for flares on dMe stars. Simultaneous GINGA and optical spectroscopy of a flare on the RS CVn star II Peg extends the correlation a further two orders of magnitude and confirms that a common, linear, relationship applies to all stellar and solar flares for which data is currently available. The significance of the result for various flare models is discussed.