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Title: High resolution studies of interstellar and stellar absorption lines in the optical spectra of OB-type stars
Author: McEvoy, Catherine Maria
ISNI:       0000 0004 6057 2000
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2016
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The study of massive stars and the interstellar medium (ISM) is fundamental to our understanding of the universe. High-resolution, high signal-to-noise ratio OB-type spectra have been analysed to investigate the structure of the intervening ISM on very small scales, the origins of B-type Galactic runaways and the impact of binarity on blue supergiants in the Large Magellanic Cloud. The structure of the diffuse ISM on scales ^1 pc is poorly understood. Interstellar absorption lines observed towards 0 - and B-type stars at multiple epochs have been compared to search for variations caused by the transverse motion of the star, combined with changes in the structure of the foreground ISM. From the analysis, it would seem that structures on scales £ 360 au do exist, but are not common phenomena. There are two accepted mechanisms to explain the origin of B-type runaway stars. The binary supernova scenario (BSS) and the cluster ejection scenario (CES). This study used the nitrogen abundance of the ejected stars, (which should be enhanced by binary transfer in the case of the BSS) to assess the relative importance of the accepted mechanisms. The CES was found to be more prevalent in the Milky Way with only one of the 38 stars analysed showing evidence for the BSS. The first comparative study of single and binary B-type supergiants is also presented. Atmospheric parameters and nitrogen abundances have been estimated for B-type supergiants identified in the VLT-FLAMES Tarantula Survey. The results have been analysed to investigate the role of binarity in the evolutionary history of supergiants. It was found that the main sequence may be significantly wider than previously assumed, extending to Teff = 20 000 K. Some marginal differences in single and binary atmospheric parameters and abundances have been identified, implying non-standard evolution for some of the sample.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available