The Physical Parameters of Four WC-type Wolf-Rayet Stars in the Large Magellanic Cloud: Evidence of Evolution*

被引:10
作者
Aadland, Erin [1 ,2 ]
Massey, Philip [1 ,2 ]
Hillier, D. John [3 ,4 ]
Morrell, Nidia [5 ]
机构
[1] No Arizona Univ, Dept Astron & Planetary Sci, Flagstaff, AZ 86011 USA
[2] Lowell Observ, 1400 W Mars Hill Rd, Flagstaff, AZ 86001 USA
[3] Univ Pittsburgh, Dept Phys & Astron, 3941 OHara St, Pittsburgh, PA 15260 USA
[4] Univ Pittsburgh, Pittsburgh Particle Phys Astrophys & Cosmol Ctr P, 3941 OHara St, Pittsburgh, PA 15260 USA
[5] Carnegie Observ, Las Campanas Observ, Casilla 601, La Serena, Chile
基金
美国国家科学基金会;
关键词
ELECTRON-IMPACT-EXCITATION; EFFECTIVE COLLISION STRENGTHS; BLANKETED MODEL ATMOSPHERES; RADIATION-DRIVEN WINDS; ATOMIC DATA; OPACITY CALCULATIONS; IRON PROJECT; OSCILLATOR-STRENGTHS; RATE COEFFICIENTS; MASSIVE-STAR;
D O I
10.3847/1538-4357/ac3426
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present a spectral analysis of four Large Magellanic Cloud (LMC) WC-type Wolf-Rayet (WR) stars (BAT99-8, BAT99-9, BAT99-11, and BAT99-52) to shed light on two evolutionary questions surrounding massive stars. The first is: are WO-type WR stars more oxygen enriched than WC-type stars, indicating further chemical evolution, or are the strong high-excitation oxygen lines in WO-type stars an indication of higher temperatures. This study will act as a baseline for answering the question of where WO-type stars fall in WR evolution. Each star's spectrum, extending from 1100 to 25000 angstrom, was modeled using cmfgen to determine the star's physical properties such as luminosity, mass-loss rate, and chemical abundances. The oxygen abundance is a key evolutionary diagnostic, and with higher resolution data and an improved stellar atmosphere code, we found the oxygen abundance to be up to a factor of 5 lower than that of previous studies. The second evolutionary question revolves around the formation of WR stars: do they evolve by themselves or is a close companion star necessary for their formation? Using our derived physical parameters, we compared our results to the Geneva single-star evolutionary models and the Binary Population and Spectral Synthesis (BPASS) binary evolutionary models. We found that both the Geneva solar-metallicity models and BPASS LMC-metallicity models are in agreement with the four WC-type stars, while the Geneva LMC-metallicity models are not. Therefore, these four WC4 stars could have been formed either via binary or single-star evolution.
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页数:26
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