Catalog Photometry and Measuring Cosmic Distances with the ROTSE-I δ Scu’s

Our current project furthers the study of the ROTSE-1 sample of δ Scu’s to provide internal structure constraints on the stars, and to test their Period-Luminosity relation. Precise photometry from individual observations supports this and enables greater sensitivity to cleanly uncover δ Scuti higher-order oscillation modes. We take these measurements under different atmospheric conditions, lunar illumination of the sky, and sometimes varying instrumental performance. Each of these can change the measurements from their value when taken under ideal conditions. We therefore require an absolute calibration, which can be achieved through the comparison of reference stars to a catalog from a calibrated telescope, which has been the PanSTARRS catalog in this instance. This entailed matching ROTSE stars to the catalog and excluding galaxies from the sample. Once achieved, we will examine the performance of the ROTSE-I magnitudes in comparison with the catalog for the reference stars, building an understanding of the most effective filtered (or unfiltered) magnitude to calibrate to. All 10 stars will then be rephased to establish the primary pulsation period.