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Mass loss from hot, luminous stars

Burnley, Adam Warwick; (2003) Mass loss from hot, luminous stars. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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A general enquiry into the physics of mass loss from hot, luminous stars is presented. Ha spectroscopy of 64 Galactic early-type stars has been obtained using the telescopes of the Isaac Newton Group (ING) and the Anglo-Australian Observatory (AAO). The sample was selected to include objects with published radio and/or mm fluxes. The Hα observations are quantitatively modelled using a modified version of the FORSOL code developed by Puls et al. (1996). FORSOL has been coupled with the PIKAIA subroutine (Charbonneau and Knapp, 1996) to create PHALTEE (Program for Hα Line Transfer with Eugenic Estimation), in order to search a specified parameter space for the 'best' (quasi- least-squares) model fit to the data, using a genetic algorithm. This renders Ha modelling both more objective and automated. Where possible, both mass-loss rates and velocity field β-exponents are determined for the sample. New mm-wave observations of nineteen Galactic early-type stars, including a subset of the Hα sample, have been obtained using the Sub-millimetre Common User Bolometer Array (SCUBA). Where possible, mean fluxes are calculated, and these data used with the results of a literature survey of mm and cm fluxes to determine mass-loss rates for a larger sample, of 53 Galactic early-type stars. The incidence of nonthermal emission is examined, with 23% of the sample exhibiting strong evidence for nonthermal flux. The occurrence of binarity and excess X-ray emission amongst the nonthermal emitters is also investigated. For the subset of 36 stars common to both the Hα and mm/radio samples, the results permit a comparison of mass-loss rates derived using diagnostics that probe the wind conditions at different radial depths. A mean value of log (Mradio/MHα) = 0.02 ± 0.05 is obtained for the thermal radio emitters. The wind-momentum-luminosity relationship (WLR) for the sample is also investigated.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Mass loss from hot, luminous stars
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Pure sciences; Galactic early-type stars
URI: https://discovery.ucl.ac.uk/id/eprint/10097786
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