Binarity and the B[e] phenomenon : investigating massive star populations in the Magellanic clouds

• Main Author: Dunstall, Paul Robert
• Published: Queen's University Belfast 2013
• Subjects: 523.112
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.601443

The body of this thesis looks at two large observational programmes: The VLT-FLAMES Survey of Massive Stars (VFSMS) and The VLT-FLAMES Tarantula Survey. The VFSMS aimed to advance the current understanding of massive star evolution by pressing the issue of rotational mixing for a sample of over 700 early type stars in the Galaxy and Magellanic Clouds. The YFTS is an extension of the VFSMS to study, in detail , the comparison of binary and single massive stars. A detailed investigation into several different massive star populations is given, from both the VFSMS and the VFTS. The work of the VFSMS is focused on a sample of 64 Be-type stars within the Magellanic Clouds . Atmospheric parameters and photospheric abundances have been used to show the Be-type star sample is inconsistent with stars rotating close to critical velocity. The VFTS investigates the number of B-type binary systems within the 30 Doradus region of the LMC, by using a cross correlations analysis technique. A binary fraction of 29% is determined from over 500 B-type stars, further refined to a true binary fraction of 66% by modelling the sample incompleteness. From the binary search, investigations are presented into three high radial velocity variable stellar objects. Firstly a study highlights the B[e] phenomenon through the analysis of the supergiant B[e ]-like binary, VFTS698. Secondly a detailed analysis of two Tare blue supergiant binary systems, VFTS450 and VFTS652 is undertaken. Finally consideration is given to the remaining B-type star samples of the VFTS that require further investigation, viz. the projected rotational velocity distribution of binaries, and the potential short-period binary systems.