Tandem superflare observations reveal origin of the stellar Fe Kα line

The Fe Kα line, or iron Kα line, is often used in astronomical research to understand the physical composition of astronomical objects. This line is produced when a K-shell electron of an iron ion in the photosphere—the gas on the stellar surface—is ejected by an external process, and has been detected in X-ray spectra of solar and stellar flares. Yet the dominant mechanism behind this ionization process has remained an open question for many years.