55082
doi
10.5281/zenodo.55082
oai:zenodo.org:55082
user-astrothesis
de Koter, Alex
University of Amsterdam
Kaper, Lex
University of Amsterdam
Sana, Hugues
KU Leuven
The properties of low-metallicity massive stars
Tramper, F.
University of Amsterdam
doi:10.1088/2041-8205/741/1/L8
doi:10.1051/0004-6361/201322155
doi:10.1051/0004-6361/201424312
doi:10.1051/0004-6361/201425390
info:eu-repo/semantics/openAccess
Creative Commons Attribution 4.0 International
https://creativecommons.org/licenses/by/4.0/legalcode
Massive stars
Wolf-Rayet stars
<p>My thesis has two main topics: the study of low-metallicity massive stars, and the study of the suspected final stage of massive stars from a certain initial mass range, the WO stars. All the data that has been used in this thesis has been obtained with the X-Shooter spectrograph on ESO's Very Large Telescope.<br />
As the formation of massive stars was favored in the metal-free early universe, the properties and evolution of low-metallicity massive stars gives insight in the influence of these stars in the young universe. I have quantitatively analyzed six O-type stars in the low-metallicity dwarf galaxies IC1613, WLM and NGC3109. These stars appear to have surprisingly strong winds, and do not agree with theoretical predictions. The analysis of four more O stars confirms this finding. The low-metallicity temperature scale, recent star formation history of the galaxies and the evolutionary state of the O stars are also discussed.<br />
The enigmatic WO stars are very rare (only 9 are known), and are thought to represent the final stage of some of the most massive stars. The spectra of most of these stars have never been modeled in detailed using expanding atmosphere codes. I have modeled the spectrum of the low-metallicity WO star DR1 and find abundances comparable to carbon Wolf-Rayet stars, but a much higher stellar temperature. The study of the other known single WO stars (5 in total) shows that most of them show very high carbon and oxygen abundances, and have less then 40% of helium left (by mass). The found stellar abundances will be used to constrain the initial masses of the stars and their evolutionary path. They are also used to constrain the illusive carbon to oxygen thermonuclear reaction rate.</p>
Zenodo
2014-11-28
info:eu-repo/semantics/doctoralThesis
636748
user-astrothesis
1579539476.691319
42636354
md5:bc710a8b6fde95b3b7e1f8cfed1b503b
https://zenodo.org/records/55082/files/thesis.pdf
public
10.1088/2041-8205/741/1/L8
Has part
doi
10.1051/0004-6361/201322155
Has part
doi
10.1051/0004-6361/201424312
Has part
doi
10.1051/0004-6361/201425390
Has part
doi
isVersionOf
doi