Date

2013

Document Type

Dissertation

Degree

Doctor of Philosophy

Department

Physics

First Adviser

McSwain, M. Virginia

Other advisers/committee members

McCluskey, George E.; Huennekens, John P.; Gunton, James D.; Stavola, Michael; Hart, Terry J.

Abstract

In this dissertation we present a study of the B and Be star populations of the Double Cluster h and χ Persei. Classical Be stars are best known for their circumstellar disks, which are composed of material ejected off of the stellar surface during outburst events. These open clusters present an optimal location for studying the physical properties and variability of these disk structures, as upwards of 30% of the brightest B–type stars in h and χ Per are known to be Be stars.To begin our study, we first need to establish reliable measurements of basic physical parameters for each B–type and Be star in our sample. Blue optical spectroscopy is used to first measure projected rotational velocity, V sin i, effective surface temperature, Teff, and surface gravity, log g, for B–type sample stars, while available Stromgren photometry is used to calculate Teff and log g for the Be stars showing emission. Stellar masses and radii are then determined for each star via the evolutionary tracks of Schaller et al. [1992].With these measurements, the model B–type star spectral energy distributions of Lanz & Hubeny [2007], and photometric observations in the optical, near– and mid–IR wavelengths, we then use two independent means of determining the distance to each star, and compare these to the established cluster distances from the study of Currie et al. [2010]. This serves as a check of the reliability of our parameter determinations and our ability to model the total stellar flux of these B–type stars.Our study of the cluster Be stars is continued by examining the disk spectral energy distributions via photometric observations from WEBDA, 2MASS, Spitzer, AKARI, and WISE. Using the methods we have developed for modeling B star stellar flux, we can now extract the Be disk contribution to the total system flux. We also present multiple observations of Hα taken between 2009–2012 with the KPNO Coudé Feed, KPNO 2.1m, and WIRO telescopes, used to monitor the presence of disk emission and its strength in our sample Be stars. We use the Hα equivalent width model of Grundstrom & Gies [2006] and the infrared flux model of Touhami et al. [2011] to constrain the disk masses, radii, and densities for our Be star sample. We find that our sample Be stars have disks 10–100 RSun in size, have densities typical of other observed Be disks, and that nearly all exhibit some level of variability in the size and strength of their disks over the course of our observations.

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