Non-LTE analysis of subluminous O-stars. VI. Feige 110.

Abstract

An analysis of the ultraviolet (1150-2000 A) and the blue 4000-5100 A) spectra of the subdwarf O-star Feige 110 is presented. Effective temperature, gravity and helium abundance of Feige 110 are determined on the basis of NLTE model atmospheres. The effective temperature of Feige 110 is found to be 40,000 K (+5000 or -3000 K). Helium abundances in the star were deficient, between 1 and 6 percent. The abundances of carbon and nitrogen were obtained from the ultraviolet resonance lines C IV and N V. The nitrogen abundance was found to be close to that of the sun but carbon was extremely deficient. Si IV resonance lines were absent in the UV spectrum of Feige 110. It is suggested that the abundance pattern of Feige 110 may have been affected by diffusion, and that, therefore, the photospheric abundance of helium, carbon, and silicon may have been larger before the onset of diffusion.