The ``Baldwin Effect'' in Wolf-Rayet Stars

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Session 46 -- Late Type Stars
Display presentation, Wednesday, 9:20-6:30, Heller Lounge Room

[46.23] The ``Baldwin Effect'' in Wolf-Rayet Stars

Patrick Morris (JILA), Peter S. Conti (JILA), H.J.G.L.M. Lamers (SRON, Utrecht), Gloria Koenigsberger (UNAM, M\`exico)

The equivalent widths of a number of emission lines in the spectra of WN-type Wolf-Rayet stars are found to inversely correlate with the luminosity of the underlying continuum. This is the well-known Baldwin Effect that has previously been observed in quasars and some Seyfert I galaxies. The Effect can be inferred from line and continuum predictions in published non-LTE model helium atmospheres and is explainable in terms of differences in wind density among WN stars. Using a simple wind model, we show that the Effect arises from a similar dependence of the continuum (free-free) opacity and the line emission on density and temperature, $\sim \rho^2 T^{-3/2}$. The Effect provides a new method for distance determinations of W-R stars.

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