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The Evolutionary Status of WN3/O3 Wolf-Rayet Stars

Published online by Cambridge University Press:  28 July 2017

Kathryn F. Neugent Open the ORCID record for Kathryn F. Neugent [Opens in a new window] ,
Phil Massey Open the ORCID record for Phil Massey [Opens in a new window] ,
D. John Hillier  and
Nidia I. Morrell
Kathryn F. Neugent
Affiliation:
Lowell Observatory, 1400 W Mars Hill Road, Flagstaff, AZ 86001 email: kneugent@lowell.edu, phil.massey@lowell.edu Department of Physics and Astronomy, Northern Arizona University, Flagstaff, AZ, 86011-6010
Phil Massey
Affiliation:
Lowell Observatory, 1400 W Mars Hill Road, Flagstaff, AZ 86001 email: kneugent@lowell.edu, phil.massey@lowell.edu Department of Physics and Astronomy, Northern Arizona University, Flagstaff, AZ, 86011-6010
D. John Hillier
Affiliation:
Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 email: hillier@pitt.edu
Nidia I. Morrell
Affiliation:
Las Campanas Observatory, Carnegie Observatories, Casilla 601, La Serena, Chile email: nmorrell@lco.cl
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Abstract

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As part of a multi-year survey for Wolf-Rayet stars in the Magellanic Clouds, we have discovered a new type of Wolf-Rayet star with both strong emission and absorption. While one might initially classify these stars as WN3+O3V binaries based on their spectra, such a pairing is unlikely given their faint visual magnitudes. Spectral modeling suggests effective temperatures and bolometric luminosities similar to those of other early-type LMC WNs but with mass-loss rates that are three to five times lower than expected. They additionally retain a significant amount of hydrogen, with nitrogen at its CNO-equilibrium value (10× enhanced). Their evolutionary status remains an open question. Here we discuss why these stars did not evolve through quasi-homogeneous evolution. Instead we suggest that based on a link with long-duration gamma ray bursts, they may form in lower metallicity environments. A new survey in M33, which has a large metallicity gradient, is underway.

Keywords

stars: Wolf-RayetMagellanic Clouds
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 12 , Symposium S329: The Lives and Death-Throes of Massive Stars , November 2016 , pp. 176 - 180
Copyright
Copyright © International Astronomical Union 2017 

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