3899 20190125155403.0 10.3390/galaxies6040131 DOI SCART-2019-0068 Van de Steene, G. C. Spectroscopic and Photometric Variability of Three Oxygen Rich Post-AGB “Shell” Objects 2018 Light, color, and radial velocity data (2007–2015) for HD 161796, V887 Her, and HD 331319, three oxygen-rich post-AGB stars, have thus far not provided direct support for the binary hypothesis to explain the shapes of planetary nebulae and severely constrain the properties of any such undetected companions. The light and velocity curves are complex, showing similar periods and variable amplitudes. Nevertheless, over limited time intervals, we compared the phasing of each. The color curves appear to peak with or slightly after the light curves, while the radial velocity curves peak about a quarter of a cycle before the light curves. Thus it appears that these post-AGB stars are brightest when smallest and hottest. The spectra of these objects are highly variable. The H α line has multiple, variable emission and absorption components. In these oxygen-rich post-AGB stars atmospheric lines, such as near-infrared Ca ii triplet and low-excitation atomic lines, also have multiple components and sometimes show line doubling, indicative of shocks induced by pulsation. GOA/ 13/ 012; BR/143/A2/STARLAB NO late-stage stellar evolution planetary nebulae multi-wavelength photometry radial velocity stellar evolution pulsation shock wave Hrivnak, B. J. Van Winckel, H. Sperauskas, J. Bohlender, D. Galaxies 6 2018 4 131-135 griet.vandesteene@observatoire.be https://www.mdpi.com/2075-4434/6/4/131/htm 1137069 http://publi2-as.oma.be/record/3899/files/postAGB_galaxies-06-00131.pdf 4319 http://publi2-as.oma.be/record/3899/files/postAGB_galaxies-06-00131.gif?subformat=icon icon 4595 http://publi2-as.oma.be/record/3899/files/postAGB_galaxies-06-00131.jpg?subformat=icon-180 icon-180 published in REFERD