Observations of Intermediate Mass Stars and their Circumstellar Environments with Nulling Interferometry

Abstract

In this dissertation, I present nulling interferometric observations of intermediate mass stars and their circumstellar environments. The observations constrain physical processes with regard to the evolution of circumstellar dust in primordial disks, as well as debris disks in main sequence objects. Observations were made in the N-band (near 10 microns) which traces primarily thermal emission from warm dust, and take advantage of the high spatial resolution afforded by nulling interferometry. The first part of the dissertation includes observations of 13 Herbig Ae stars using the BLINC-MIRAC instrument on the MMT and Magellan I (Baade) Telescopes. Three of the 13 objects were spatially resolved (AB Aurigae, HD 100546, and HD 179218). It appears that inferred disk sizes and limits are correlated to the submillimeter SED slope and fractional infrared luminosity of the objects. This implies that disk flaring may have an effect on the resolvability. Further examination of the results reveals evidence for a large inner gap in the HD 100546 disk, possibly resulting in the large inferred disk size. The second part of the dissertation includes observations of six nearby main sequence targets, all of which show no evidence for a positive detection of warm debris. Using a scaled up model of solar zodiacal emission, upper limits on dust density range from 500 to 10^4 Zody (1 Zody = the density of our own solar zodiacal cloud) depending on the particular star, which corresponds to limits of 10^-6 to 5 x 10^-5 earth masses of micron-sized dust. The well studied nature of the debris disks around Vega, epsilon Eridani, and zeta Leporis allows us to place these observations in the context of previous studies at other wavelengths to determine the physical processes responsible for shaping the debris disk in these systems.