dc.contributor.author Shultz, Matthew en dc.date 2016-07-26 15:42:31.342 dc.date 2016-08-02 12:36:18.169 dc.date.accessioned 2016-08-05T22:05:31Z dc.date.available 2016-08-05T22:05:31Z dc.date.issued 2016-08-05 dc.identifier.uri http://hdl.handle.net/1974/14691 dc.description Thesis (Ph.D, Physics, Engineering Physics and Astronomy) -- Queen's University, 2016-08-02 12:36:18.169 en dc.description.abstract How do the magnetic fields of massive stars evolve over time? Are their gyrochronological ages consistent with ages inferred from evolutionary tracks? Why do most stars predicted to host Centrifugal Magnetospheres (CMs) display no H$\alpha$ emission? Does plasma escape from CMs via centrifugal breakout events, or by a steady-state leakage mechanism? This thesis investigates these questions via a population study with a sample of 51 magnetic early B-type stars. The longitudinal magnetic field \bz~was measured from Least Squares Deconvolution profiles extracted from high-resolution spectropolarimetric data. New rotational periods $P_{\rm rot}$ were determined for 15 stars from \bz, leaving only 3 stars for which $P_{\rm rot}$ is unknown. Projected rotational velocities \vsini~were measured from multiple spectral lines. Effective temperatures and surface gravities were measured via ionization balances and line profile fitting of H Balmer lines. Fundamental physical parameters, \bz, \vsini, and $P_{\rm rot}$ were then used to determine radii, masses, ages, dipole oblique rotator model, stellar wind, magnetospheric, and spindown parameters using a Monte Carlo approach that self-consistently calculates all parameters while accounting for all available constraints on stellar properties. Dipole magnetic field strengths $B_{\rm d}$ follow a log-normal distribution similar to that of Ap stars, and decline over time in a fashion consistent with the expected conservation of fossil magnetic flux. $P_{\rm rot}$ increases with fractional main sequence age, mass, and $B_{\rm d}$, as expected from magnetospheric braking. However, comparison of evolutionary track ages to maximum spindown ages $t_{\rm S,max}$ shows that initial rotation fractions may be far below critical for stars with $M_*>10 M_\odot$. Computing $t_{\rm S,max}$ with different mass-loss prescriptions indicates that the mass-loss rates of B-type stars are likely much lower than expected from extrapolation from O-type stars. Stars with H$\alpha$ in emission and absorption occupy distinct regions in the updated rotation-magnetic confinement diagram: H$\alpha$-bright stars are found to be younger, more rapidly rotating, and more strongly magnetized than the general population. Emission strength is sensitive both to the volume of the CM and to the mass-loss rate, favouring leakage over centrifugal breakout. en dc.language.iso eng en dc.relation.ispartofseries Canadian theses en dc.rights Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada en dc.rights ProQuest PhD and Master's Theses International Dissemination Agreement en dc.rights Intellectual Property Guidelines at Queen's University en dc.rights Copying and Preserving Your Thesis en dc.rights This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner. en dc.rights This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner. en dc.subject Stellar Winds en dc.subject Binary Stars en dc.subject Magnetospheres en dc.subject Massive Stars en dc.subject Magnetic Braking en dc.subject Stellar Magnetism en dc.subject Spectropolarimetry en dc.title The Rotational Evolution and Magnetospheric Emission of the Magnetic Early B-type Stars en dc.type thesis en dc.description.degree PhD en dc.contributor.supervisor Wade, Gregg en dc.contributor.supervisor Rivinius, Thomas en dc.contributor.supervisor Hanes, David en dc.contributor.department Physics, Engineering Physics and Astronomy en dc.degree.grantor Queen's University at Kingston en
﻿