Optical spectrophotometry of HR 1099 during a major flare outburst

A recent outburst of the active RS CVn star HR 1099 was detected at radio wavelengths and communicated in time for simultaneous optical observations. A pair of high-dispersion (9 and 18 A/mm) spectrograms were obtained covering the wavelength region lambda3640--7000 A, and have been analyzed photometrically. Exceptionally strong emission was found at Hα and at the CaII H and K lines. All of the members of the Balmer series exhibit emission characteristics with a decrement considerably less steep than that exhibited by normal recombination radiation from gaseous nebulae. Arguments are made that nonthermal excitation mechanisms are required to account for the data