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Determination of the Interstellar Extinction Toward WN Stars from Observed UBV Color Indices

Published online by Cambridge University Press:  03 August 2017

William D. Vacca
Affiliation:
Joint Institute for Laboratory Astrophysics University of Colorado, Boulder, CO 80309-0440, USA
Werner Schmutz
Affiliation:
Joint Institute for Laboratory Astrophysics University of Colorado, Boulder, CO 80309-0440, USA

Extract

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Recent observations of Wolf-Rayet stars by Massey (1984) and Torres-Dodgen and Massey (1988) have yielded high quality, absolutely calibrated spectra of nearly all known Wolf- Rayet objects. These observations also indicate that discontinuities, or “jumps”, are present in the continuum spectra of some Wolf-Rayet stars. Such continuum jumps are predicted by the current theoretical models of Wolf-Rayet atmospheres. In general, these models provide good fits to the observed spectra of Wolf-Rayet stars. The models also indicate that, between jumps, the intrinsic continuum can be closely approximated by a power law in wavelength. In this case, we have the following relation between the intrinsic colors: where and Z3645 is the strength of the He II (η = 4) jump at 3645 Å in mags. This relation holds because the central wavelength of the u filter (λu = 3650 Å) is nearly coincident with that of the He II jump. In addition, models of WN stars with helium-dominated atmospheres predict a correlation between D3645 and (6 - v)o:

Type
Session VIII. Inventory and Distribution
Copyright
Copyright © Kluwer 1991