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Is binarity necessary for the evolution of massive stars to the luminous blue variable and Wolf-Rayet stages?

Aadland, Erin Christine (2022) Is binarity necessary for the evolution of massive stars to the luminous blue variable and Wolf-Rayet stages? Doctoral thesis, Northern Arizona University.

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The fundamental question in massive star evolution is how important binarity is in their evolution. Luminous blue variables (LBVs) and Wolf-Rayet (WR) stars are the last phases of evolution for the most massive stars and whether a close companion star is required for their evolution and what their relation is to each other is heavily debated. In single-star evolution, the most massive stars have a short-lived transitionary phase as LBVs before evolving into WR stars. In the binary evolution, LBVs are mass gainers and WRs undergo mass-loss via Roche Lobe overflow. To shed light on this fundamental question, we analyze the spatial distribution of LBVs compared to their progenitor O-type stars and descendant WR stars. We found the LBVs have a spatial distribution similar to the other massive star samples, meaning that a close companion star is not required in their formation. For WR stars, we model the near-infrared, optical, and ultraviolet spectrum of carbon-rich (WC-type) and oxygen-rich (WO-type) WR stars to determine their physical parameters, which can be compared to those predicted by the Geneva single-star and BPASS binary evolutionary models. The WC- and WO- type stars have successes and problems with both types of evolution, possibly also indicating that they could have evolved as single stars. Through this process, the WOs were found to be further evolved than the WCs confirming that they are the last ``hurrah'' of massive star evolution. Overall, massive stars may not require a close companion star to form and evolve.

Item Type: Thesis (Doctoral)
Publisher’s Statement: © Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords: Luminous Blue Variables; Massive Stars; Stellar Evolution; Wolf-Rayet
Subjects: Q Science > QB Astronomy
NAU Depositing Author Academic Status: Student
Department/Unit: Graduate College > Theses and Dissertations
College of the Environment, Forestry, and Natural Sciences > Physics and Astronomy
Date Deposited: 13 Jul 2022 16:51
Last Modified: 13 Jul 2022 16:51
URI: https://openknowledge.nau.edu/id/eprint/5839

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