Multi-pronged investigations into exoplanetary magnetic fields
Wilson Cauley (Arizona State University)
Efforts in exoplanet characterization have led to some very precise determinations of planetary densities, compositions, and even accurate maps of active region and spot locations on stellar surfaces. Exoplanet magnetic fields, however, remain elusive. While radio observations continue to push into the low-mass brown dwarf regime, no emission from a planetary-mass object has been confirmed. I will discuss some of the efforts involving alternate methods for probing exoplanet magnetic fields and how they stack up so far against the prospects for detection via radio emission.
The Circumstellar Disks and Binary Companions of Be Stars
Drew Chojnowski, NMSU
Tremendous progress has been made over the past two decades toward understanding Be stars, but a number of key aspects of them remain enigmatic. The unsolved mysteries include identification of the mechanism responsible for disk formation, the reason this mechanism occasionally turns off or on unexpectedly, the source of viscosity in the circumstellar disks, and the cause of slowly precessing density perturbations in the disks of many or most Be stars. On a deeper level, the origin of Be stars’ near-critical rotation is unknown, with one possible explanation being spin-up due to interaction with a binary companion. A better understanding of these stars is needed, with a particular focus on high-mass binaries being warranted in the age of gravitational wave astronomy. In this dissertation, I will extend the knowledge and understanding of Be stars through a series of three projects. First, I will present and describe the largest ever homogeneous, spectroscopic sample of Be stars to date. I will then focus on investigation of a rare class of Be stars found in binary systems with hot, low mass companions. The second project will present detailed characterization and modeling of HD~55606, a newly discovered member of this class. Finally, I will discuss the results of spectroscopic monitoring of seven newly discovered systems and establish or place limits on the orbital parameters of the binary components.