An Investigation Of Six Poorly Described Close Visual Double Stars Using Speckle Interferometry
Date of Award
Master of Science (MS)
Paul S. Hardersen
Continued observation of double stars is necessary for confirmation of binarity and to provide updates to astrometric data used to compute accurate binary orbital parameters, thereby more accurately informing stellar mass estimations – the critical parameter from which stellar models are derived. In October of 2013, six double stars from the Washington Double Star (WDS) catalog exhibiting close separations, as well as significant deviations from previously published orbits, were observed and imaged using the speckle interferometric technique on the 2.1-meter telescope at Kitt Peak National Observatory (KPNO) in Arizona. The observations of the six double stars occurred as part of large, collaborative, eight-night, student-learning-centered observing run organized by principal investigator Genet of California Polytechnic Institute. The run produced in total roughly 1000 raw speckle images for each of the more than 1000 double stars and single reference stars observed, resulting in a total database of 1.4 terabytes. The speckle images for the targets, including the six targets investigated in this thesis, were taken using a relatively low-cost, portable speckle interferometry camera system developed by Genet, the heart of which is a lightweight, high speed, high signal to noise ratio (SNR) Andor electron multiplying CCD (EMCCD) camera capable of exposures on the order of tens of milliseconds. Exposures of 10-20 milliseconds are faster than atmospheric coherence timescales, and allow for the implementation of the speckle interferometry – the obtainment of diffraction-limited image information of binary stars defined by the full aperture of the telescope from the autocorrelation and Fourier analysis of randomly distributed, isoplanatically correlated speckle pairs, which represent the diffraction-limited images of the associated coherence cells above and within the atmospheric area of the primary aperture (sub-apertures). Following the Oct. 2013 observing run, reduction and analysis of the speckle images for the six target binary stars (as well as five calibration binaries) and determination of the new astrometry was completed using the general purpose astrometry software program PlateSolve3 (PS3), written and developed by Rowe & Genet (2014). Using the new astrometric data derived from the Oct. 2013 2.1-meter speckle observations, the previously published United States Naval Observatory (USNO) orbital plots for the six target doubles were updated to reflect the new, and in some cases missing measurements. Target double star orbits were reevaluated in light of the updates in order to draw conclusions about the characteristics of each proposed binary system. In all six target cases, continued trends in significant astrometric deviations from published orbits and ephemerides have been demonstrated by the new observations, indicating the need for orbital revisions of these binaries. Analysis of systems WDS22357+5413, WDS02231+7021, and WDS06256+2227 indicate rectilinear rather than Keplerian motion, and are concluded to likely be optical doubles. As a result of this work, two observations of WDS05153+4710 were shown to be erroneous and have been scheduled to be removed from this binary’s WDS observational record (Mason, private communication, 2015). Complementary to the central goal of investigating the six target close visual double stars via speckle interferometry, the entire effort demonstrated the applicability and utilization of relatively low-cost portable speckle camera systems on large telescopes, as well as the value and advantages of student participation and contribution within the realm of a large-scale observing run at a major observatory and the resulting peer reviewed scientific works that follow.
Wallace, Daniel B., "An Investigation Of Six Poorly Described Close Visual Double Stars Using Speckle Interferometry" (2015). Theses and Dissertations. 1849.