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The e-MERLIN L-band Legacy Survey of Cygnus OB2

Morford, JC; (2017) The e-MERLIN L-band Legacy Survey of Cygnus OB2. Doctoral thesis , UCL (University College London). Green open access

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The Cygnus OB2 Radio Survey (COBRaS) is an e-MERLIN Legacy survey awarded ~ 300 hours worth of observing time. Split between L-(42 hrs) and C-(252 hrs) band, the project aims to push the limits of e-MERLIN’s enhanced capabilities by providing highly sensitive, targeted, deep-field radio maps of the core of the Cygnus OB2 association. The L-band (21cm) observations, completed throughout the Spring of 2014, serve as the focus of the work presented here. This thesis primarily aims to investigate the radio emission from massive (M 8 M⊙ ) stars in the Cyg OB association, in order to obtain a better understanding of their mass-loss rates and binarity. A description of the entire data reduction process of the COBRaS 21cm observations is given, as is a discussion of the mitigation of radio frequency interference (RFI). In the advent of new radio telescopes, the technical skills, research and tools developed throughout this process aims to serve the wider radio astronomy community. Further technical work is presented in the form of novel source extraction and cross-correlation scripts that deliver the COBRaS L-band all source catalogue (CLASC). Reaching resolutions of ~180 mas, precise positions and 21cm flux densities are presented for 41 sources found within a 0.48 x 0.48 deg region, centred on the Cyg OB2 association. In obtaining a 3σ sensitivity limit of ~ 100 μJy, these observations significantly improve upon previous surveys of the region. Accurate determinations of the mass-loss rates of single massive OB stars are used to investigate their stellar wind properties, helping to resolve current discrepancies in the mass-loss rates via clumped and structured hot star winds. Finally, an analysis of the non-thermal radiation from the colliding winds of massive star binaries seeks to clarify our understanding of such systems and their radio emission processes.

Type: Thesis (Doctoral)
Title: The e-MERLIN L-band Legacy Survey of Cygnus OB2
Event: University College London
Open access status: An open access version is available from UCL Discovery
Language: English
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/1549637
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