Hackman, Thomas

Contact Email: Thomas.Hackman@helsinki.fi
Institute: Observatory, University of Helsinki
First Coauthor: Lauri Jetsu
Institute: Observatory, University of Helsinki
Presenting Thesis: Yes
Subject Area: Stellar Atmospheres, Circumstellar Material
Waveband: Optical
Technique: Imaging (Doppler)
Presentation: Poster Display
Title: Surface imaging of HD 199178: High latitude spot and differential rotation
Abstract: We present surface (Doppler) imaging temperature maps of the FK Comae-type star HD 199178 (V1794 Cyg). The maps were calculated from high resolution spectra and simultaneous Johnson V-photometry between 1994 and 1997. All maps reveal a high latitude spot, which is 1200-1600 K cooler than the mean surface temperature. The observed slightly flat bottomed absorption lines could be explained by antisolar surface differential rotation. Time series analysis of partly simultaneous photometry shows a varying photometric rotation period, which indicates differential rotation.