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Full-Text Articles in Stars, Interstellar Medium and the Galaxy
Nitrogen Abundances In Early-Type Be Stars, Ahmed Ahmed
Nitrogen Abundances In Early-Type Be Stars, Ahmed Ahmed
Electronic Thesis and Dissertation Repository
A sample of 26 Be stars from the Magnetism in Massive Stars (MiMeS) spectroscopic survey are analyzed for their photospheric nitrogen abundances in an effort to detect rotational mixing in the Be stars. Be stars are massive stars, between 3 and 20 times the mass of the Sun, that are surrounded by a thin, equatorial disk of gas that produces emission lines in their optical and near-infrared spectra. Be stars are the most rapidly-rotating stellar population on the main sequence, where stars produce energy by core hydrogen burning. New, non-LTE line transfer calculations are performed for the Nii ion, the …
Stellar Spectroscopy: New Methods And Insights, Sanaz S. Golriz
Stellar Spectroscopy: New Methods And Insights, Sanaz S. Golriz
Electronic Thesis and Dissertation Repository
The study of the chemical evolution of stars is of crucial importance since they play a major role in the enrichment of the chemistry of the universe. Throughout their lifetime, stars undergo several processes that can alter their chemistry. Gradually, the nucleosynthesis products from the interior of the star are radiatively and convectively levitated and mixed with the upper layers of the atmosphere. In the later stages of their evolution, low to intermediate mass stars (0.8-8.0~M☉) eject a significant fraction of these nucleosynthesis products, resulting in a circumstellar envelope of gas and dust around the central star with a very …
Methods And Results Toward Measuring Magnetic Fields In Star-Forming Regions, Scott C. Jones
Methods And Results Toward Measuring Magnetic Fields In Star-Forming Regions, Scott C. Jones
Electronic Thesis and Dissertation Repository
Star formation is a fundamental process in the evolution of the cosmos. Yet given the abundance of stellar constituents, it remains prescient as to why the number of stars is not correspondingly large. If we cannot satisfactorily explain how stars are formed, then many further avenues of research are hindered. This thesis makes claims about one of the foremost theories as to the relative lack of stars, interstellar magnetic fields. These fields have been observationally verified on multiple scales. I will use the most direct method to probe magnetic fields in known star-forming regions, polarization, at millimetre/submillimetre wavelengths. In particular …