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Displaced He I absorption lines in Wolf-Rayet stars: revisions to υ∞?

1989; Oxford University Press; Volume: 240; Issue: 2 Linguagem: Inglês

10.1093/mnras/240.2.445

1365-2966

P. M. Williams, P. Eenens,

Astro and Planetary Science

New 2-μm spectra of eight Wolf-Rayet stars are presented, showing He I|$2{s}^{1} S-2{p}^{1} {P}^{\circ}$| absorption lines displaced by velocities ~ 0.7 of the terminal velocities derived conventionally. It is argued that these lines are formed in the outermost regions of the winds and give more accurate representations of the terminal velocities than do the violet edges of the P Cygni profiles of C IV observed in the UV. Consequently, mass loss rates derived for these stars using the C IV profiles must be reduced in proportion. From the similarity of their displacement velocities to those of the He I lines, it is suggested that the narrow Fe III absorption lines observed in we 9 stars are also formed in the asymptotic region and are neither related to the NACs seen in other luminous early-type stars nor formed in distant wind deceleration zones.