Winds in hot, subluminous stars

Ultraviolet spectra over the wavelength range 1150 to 1750 A of the nuclei of two planetary nebulae are used to derive information concerning their winds. The nucleus of NGC 6826 is a 10th magnitude star with an O3f-type spectrum, an apparent terminal wind velocity of 2000 km/s, and a general level of ionization similar to that in Zeta Pup. The nucleus of Abell 78 is a 13th magnitude star having an OVI-type spectrum, an effective temperature between 100,000 and 150,000 K, and a gravity greater than 100,000 cm/second squared. Its apparent terminal wind velocity is 3400 km/s, and it has a very high general level of ionization. It is suggested that a luminosity-to-mass ratio (in solar units) greater than about 1600 is now an applicable mass-loss criterion for all hot stars, including planetary nuclei.