Analysis of Zeta Ophiochi Using Stellar Intensity Interferometry

Stellar intensity interferometry (SII), developed first by Robert Hanbury Brown and Richard Twiss in the 1950s, measures the correlation of light intensity fluctuations from a star using multiple detectors at various baselines. The Very Energetic Radiation Imaging Telescope Array System (VERITAS) at Fred Lawrence Whipple Observatory (FLWO) has four Imaging Air Cherenkov Telescopes (IACT) with projected baselines ranging from 30-180 m which are used to measure the size and oblateness of bright stellar photospheres. Using this array, VERITAS has contributed to the revitalization of SII and has accumulated 25 hours of data on ζ Ophiuchi, a rapid rotator with a measurable oblateness. We have extracted a preliminary measurement of the oblateness of the photosphere and I will present details of the analysis and identification of environmental contamination of the data that has gone into this measurement.