Ultraviolet Extinction of Circumstellar Dust in HD 45677

Abstract

The far-UV extinction towards a B[e] star has at least two components: interstellar and circumstellar. The observed absorption in the visible and UV range due to circumstellar dust is a medley effect of absorption and scattered stellar radiation light (4), so that its distribution is flatter as it would correspond to dust particles described by high values of R ^V = A ^V/E(B - V) (ratio of total to selective extinction). The aim of this paper is to study whether it is possible to model the observed far-UV (from 0.12µm to 0.31µm) absorption A ^λ of B[e] stars with a unique biparametric representation as given by (1): A ^λ = a(λ) x A ^V+ b(λ) x E(B - V), where A ^V= A ^ISM _V + A ^CSD _V , E(B - V) = E(B-V) _ISM + E(B - V) _CSD (ISM stands for interstellar component and CSD for circumstellar dust) and a(λ), b(λ) are universal interpolatory functions. We used archive IUE data for HD 45677. As comparison star we used HD 64802 (B2V, E(B-V) = 0.05).