Hydrogen-free Wolf-Rayet stars: Helium stars with envelope-inflation structure and rotation
文献类型：期刊论文
| 作者 | Lu, Xizhen2,3; Zhu, Chunhua3 ; Liu, Helei3; Guo, Sufen3; Yu, Jinlong1,3; Lu, Guoliang2,3
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| 刊名 | ASTRONOMY & ASTROPHYSICS
 |
| 出版日期 | 2023-06-23 |
| 卷号 | 674页码:9 |
| ISSN号 | 0004-6361 |
| 关键词 | stars: Wolf-Rayet stars: rotation stars: mass-loss |
| DOI | 10.1051/0004-6361/202243188 |
| 通讯作者 | Zhu, Chunhua(chunhuazhu@sina.cn) |
| 英文摘要 | Context. Observations have shown that the effective temperature of hydrogen-free Wolf-Rayet (WR) stars is considerably lower than that of the standard model, which means that the radius of the observed H-free WR stars is several times larger than that estimated by the standard model. The envelope inflation structure (EIS) caused by the radiation luminosity being close to the Eddington luminosity in the iron opacity peak region of H-free WR stars may be the key to resolving the radius problem of H-free WR stars. Aims. We study the structure and evolution of helium (He) stars with the EIS and discuss the influence of rotation on these He stars. We aim to explain the radius problem of H-free WR stars observed in the Milky Way (MW) and the Large Magellanic Cloud (LMC) through the He stars. Methods. Using the Modules for Experiments in Stellar Astrophysics code, we compute the evolution of He stars with and without MLT++ prescriptions, and discuss their effects on the EIS. We calculated the evolution of He stars using a new mass-loss rate formula and three different relative rotational velocities and compared our results with observations on Hertzsprung-Russell diagrams. Results. The EIS has different effects on the structure and evolution of He stars with different masses. Due to the luminosity well below the Eddington limit, low-mass He stars with an initial mass of less than 12 M-circle dot do not produce EIS with or without the MLT++ prescription. High-mass He stars with an initial mass exceeding 12 M-circle dot and without the MLT++ prescription produce the EIS. Since the EIS is Eddington factor G-dependent, its radius increases with the increase in metallicity and decreases with rotational velocity increase. For rotating low-mass He stars, since the rotational mixing timescale is smaller than the evolutionary timescale, rotational mixing can increase the lifetime and allow He stars to evolve into WC stars during the helium giant phase. For rotating high-mass He stars, since rotation increases the mass-loss rate, the radius of the EIS decreases as rotational velocity increases. The rotation-decay timescale of rapidly rotating He stars is very short, and the rapidly rotating He stars only appear within the first one-tenth of their lifetime, which is consistent with the observations of WR stars. Conclusions. The low-luminosity (log(L/L-circle dot) = 5.2) H-free WR stars in the MW and the LMC can be explained by the helium giant phase in low-mass He stars, the high X-C and X-O in WC stars can only evolve through low-mass He stars with a rapid rotation. High-mass He stars with the EIS can explain H-free WR stars with a luminosity exceeding 10(5.7) L-circle dot and an effective temperature above 10(4.7) K in the MW. They can also explain H-free WR stars on the right-hand side of the He zero-age main sequence in the LMC. High-mass stars with the EIS evolve into WO stars at the final evolution stage, and the shorter lifetime fraction is consistent with the small number of observed WO stars. |
| WOS关键词 | LINE-DRIVEN WINDS ; MASS-LOSS RATES ; PRESUPERNOVA EVOLUTION ; METALLICITY DEPENDENCE ; STELLAR PARAMETERS ; SPECTRAL-ANALYSES ; GALACTIC WC ; MODULES ; POPULATIONS ; DISTANCES |
| 资助项目 | National Natural Science Foundation of China[U2031204] ; National Natural Science Foundation of China[12163005] ; National Natural Science Foundation of China[11863005] ; National Natural Science Foundation of China[2022D01D85] ; China Manned Space Project[CMS-CSST-2021-A10] ; Natural Science Foundation of Xinjiang[2021D01C075] |
| WOS研究方向 | Astronomy & Astrophysics |
| 语种 | 英语 |
| 出版者 | EDP SCIENCES S A |
| WOS记录号 | WOS:001021296000010 |
| 资助机构 | National Natural Science Foundation of China ; China Manned Space Project ; Natural Science Foundation of Xinjiang |
| 源URL | [http://ir.xao.ac.cn/handle/45760611-7/5325]  |
| 专题 | 研究单元未命名 |
| 通讯作者 | Zhu, Chunhua |
| 作者单位 | 1.Tarim Univ, Coll Mech & Elect Engn, Alar 843300, Peoples R China 2.Chinese Acad Sci, Xinjiang Astron Observ, 150 Sci 1 St, Urumqi 830011, Xinjiang, Peoples R China 3.Xinjiang Univ, Sch Phys Sci & Technol, Urumqi 830046, Peoples R China |
| 推荐引用方式 GB/T 7714 | Lu, Xizhen,Zhu, Chunhua,Liu, Helei,et al. Hydrogen-free Wolf-Rayet stars: Helium stars with envelope-inflation structure and rotation[J]. ASTRONOMY & ASTROPHYSICS,2023,674:9. |
| APA | Lu, Xizhen,Zhu, Chunhua,Liu, Helei,Guo, Sufen,Yu, Jinlong,&Lu, Guoliang.(2023).Hydrogen-free Wolf-Rayet stars: Helium stars with envelope-inflation structure and rotation.ASTRONOMY & ASTROPHYSICS,674,9. |
| MLA | Lu, Xizhen,et al."Hydrogen-free Wolf-Rayet stars: Helium stars with envelope-inflation structure and rotation".ASTRONOMY & ASTROPHYSICS 674(2023):9. |
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