The discovery of a hot companion to the K-type supergiant HD 4817.

Abstract

The discovery, through observations with the International Ultraviolet Explorer, of a B5 main sequence companion to the cool supergiant star HD 4817 (K2Ib-II) is reported. The object might be a new member of the Zeta Aur class. The UV observations indicate that HD 4817 is quite heavily reddened (E/B - V/ = 0.52) and that its distance is 1030 +/-80 pc. IUE high resolution spectra reveal the presence of two components in the resonance absorption lines of Fe II around 2600 A and in the Mg II 2800 A doublet. The lower velocity component at -9 km/s is ascribed to interstellar gas absorption. The higher velocity component at -36 km/s is ascribed to slowly expanding circumsystem material.