Hot Components and Circumstellar Grains in M Supergiant Syncretic Binaries

Abstract

The authors have aqcquired ultraviolet spectra and infrared data to study grains in cool star plus hot star syncretic (VV Cep) type binaries. Though M supergiants almost always have circumstellar grains, the authors found grains, from IRAS infrared photometry, in only about half of the syncretic systems. Infrared spectra revealed that the circumstellar grains are silicates. With the IUE ultraviolet spectra, the authors classified the hot stars and calculated residual ultraviolet extinctions. The flat extinctions confirm the lack of grains in many systems, though several systems with grains fail to show ultraviolet extinction. The IRAS and IUE results, together with measured hydrogen column densities, orbital information, and previous work, suggest that grains have not formed in many syncretic systems because of ultraviolet radiation from the hot star.