Distribution and time evolution of starspots on VW Cephei studied with Doppler imaging

grantor: University of TorontoMaximum entropy Doppler images of VW Cephei produced from seven datasets of simultaneous photometric and spectroscopic data are presented. The observations were obtained at the David Dunlap Observatory from March 11, 1991 to May 13, 1993. The photometric observations were made in the Johnson-Morgan, Kron-Cousins BVRI system, and the spectroscopic observations were made at NaD and $H\alpha$ on alternating nights. The data were reduced using algorithms requiring little or no user intervention. Algorithms for automated dispersion fitting, cosmic ray removal, and telluric line removal are presented in detail. An improvement to the Optimal Spectrum Extraction Algorithm of Horne (1986), allowing better extraction under conditions of high sky background, is presented and used. The Doppler images were produced using maximum entropy regularisation, fitting geometrical and orbital parameters of the contact binary at the same time as spots using both the spectroscopic and photometric data to constrain the models. Spots were modeled as being 3500 K in temperature, fractionally covering each surface element of the system to different amounts. These models fitted the observational data very well.Ph.D