Stars, Interstellar Medium and the Galaxy Commons^™

The Continuum Linear Polarization Signature Of Classical Be Stars, Robbie J. Halonen

Electronic Thesis and Dissertation Repository

Classical Be stars are rapidly-rotating, massive stars that exhibit distinct observational characteristics due to the presence of enveloping, equatorial disks of gas. While diligent observation of these objects has established a reliable description of their geometric and kinematic properties, our understanding of classical Be stars remains distressingly limited on the dynamical front. Principally, we lack a satisfactory characterization of the physical process(es) through which the gaseous disks form and dissipate. In order to understand the mechanisms that govern the development of these enigmatic stars, we use computational codes to produce theoretical models of these objects and their environments. We compare …

The Atmospheric Chemistry Of Magnetic Bp Stars, Jeffrey D. Bailey

Electronic Thesis and Dissertation Repository

The chemically peculiar magnetic A- and B-type (Ap/Bp) stars are characterised by large overabundances, of the order of 10^2 and 10^4 times the Sun, of Fe-peak and rare earth elements, respectively. Further, they possess strong, ordered magnetic fields (of order 1 kG) that are roughly dipolar in nature. We present in-depth investigations of magnetic Ap/Bp stars, ranging from detailed analyses of specific stars to larger surveys aimed at studying stratification and atmospheric abundance evolution.

For HD 133880 and HD 147010, we offer complete investigations of their magnetic fields and chemical abundance distributions. For each star, a simple magnetic field model …

Core Formation In Partially Ionized Magnetic Molecular Clouds, Nicole D. Bailey

Electronic Thesis and Dissertation Repository

Linear analysis of the formation of protostellar cores in planar magnetic interstellar clouds shows that molecular clouds exhibit a preferred length scale for collapse that depends on the mass-to-flux ratio and neutral-ion collision time within the cloud. This linear analysis can be used to investigate the formation of star forming clusters and the distribution of mass within star forming regions. By combining the results of the linear analysis with a realistic ionization profile for the cloud, we find that a molecular cloud may evolve through two fragmentation events in the evolution toward the formation of stars. Our model suggests that …

A Variability Study Of The Typical Red Supergiant Antares A, Teznie J D Pugh

Electronic Thesis and Dissertation Repository

Red giants and red supergiants have long been known to be variable. In the last 40 years many of the features of this variability have been associated with large convective cells. Unfortunately, due to the long timescales of these variations they are not well studied, with the exception of the bright M-class supergiant Betelgeuse (α Orionis, M2 Iab). Betelgeuse has been well studied both observationally and theoretically, and has many features that are well described by models of convection. It was these studies of Betelgeuse that provided the main motivation for this thesis. We ask if the dramatic motions seen …