Automated variable star classification and the pulsation properties of eclipsing delta Scuti stars

Variable stars are important for many physical applications. With many large sky surveys currently coming online, an efficient and reliable automated method to identify and classify variable stars is needed to sift through the terra- bytes of data. I present the results of an effort to create such a pipeline, as tested on the Northern Sky Variability Survey (NSVS). The method relies heavily on Fourier decomposition that is proven to be both relatively fast and reliable for periodic variable star identification and classification. The method successfully classifies objects in the test survey into one of five variable star classes: (1) Algol/b Lyr, (2) RR Lyr, (3) W UMa, (4) Cepheid/long-period variables, and (5) d Scuti/short-period variables. Errors in classification are relatively low and if these candidates are confirmed, the number of known W UMa, Algol/b Lyr, and galactic Cepheids will increase dramatically.

The second part of the project is to investigate the oscillating Algol (oEA) variable star class, where one component of the Algol binary is a pulsating star. I present the results of a photometric and spectroscopic observing campaign to determine the individual masses of eight oEA objects using radial velocity measurements. These are among the first direct dynamical determinations of the masses of oEA systems and d Scuti stars. It is found that the companion star to the d Scuti in these binaries can have a large effecton the pulsation frequencies and modes of the pulsating component. It is found that several of the d Scuti stars in the oEA systems have some of the shortest primary pulsation frequencies of all known d Scuti stars. There appears to be a relation in which as the orbital period of the oEA binary decreases, the the primary pulsation period also decreases. I present attempts at mode identification on several of the oEA systems and find that current stellar models fail to explain the pulsation properties of several of the systems, or can only be explained by high overtone pulsations.