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arXiv · 1701.08154

The Evolutionary Status of WN3/O3 Wolf-Rayet Stars

Kathryn F. Neugent·Phil Massey·D. John Hillier·Nidia I. Morrell
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Abstract

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 (10x 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.

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Kathryn F. Neugent, Phil Massey, D. John Hillier, Nidia I. Morrell. 2017-01-27. The Evolutionary Status of WN3/O3 Wolf-Rayet Stars. https://doi.org/10.1017/s1743921317002629

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