Interpretation of the UV spectrum of some stars with little reddening

Abstract

The UV spectrum of a few reddened stars will be decomposed into two terms. One is the direct starlight, F _★,λ⁰ e^{-τ _λ}, which is the product of the flux of the star corrected for interstellar extinction, F_{★, λ}⁰, and of the extinction e ^{- τ_λ}. The second is starlight scattered by interstellar dust into the beam of the observation. This excess of scattered starlight affects the FUV part of the spectrum ( λ<2200 Å). The combination of both terms gives the shape of the UV spectrum of a reddened star, with its characteristic depression at 2200 Å.