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Galaxies 2018, 6(4), 131; https://doi.org/10.3390/galaxies6040131

Spectroscopic and Photometric Variability of Three Oxygen Rich Post-AGB “Shell” Objects

1
Royal Observatory of Belgium, Astronomy and Astrophysics, Ringlaan 3, 1180 Brussels, Belgium
2
Department of Physics and Astronomy, Valparaiso University, Valparaiso, IN 46383, USA
3
Instituut voor Sterrenkunde, K.U. Leuven University, Celestijnenlaan 200 D, B-3001 Leuven, Belgium
4
Vilnius University Observatory, Ciurlionio 29, Vilnius 2009, Lithuania
5
National Research Council of Canada, Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
*
Author to whom correspondence should be addressed.
Received: 28 June 2018 / Revised: 28 November 2018 / Accepted: 29 November 2018 / Published: 3 December 2018
(This article belongs to the Special Issue Asymmetric Planetary Nebulae VII)
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Abstract

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. View Full-Text
Keywords: late-stage stellar evolution; planetary nebulae; multi-wavelength photometry; radial velocity; stellar evolution; pulsation; shock wave late-stage stellar evolution; planetary nebulae; multi-wavelength photometry; radial velocity; stellar evolution; pulsation; shock wave
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Steene, G.C.V.; Hrivnak, B.J.; Winckel, H.V.; Sperauskas, J.; Bohlender, D. Spectroscopic and Photometric Variability of Three Oxygen Rich Post-AGB “Shell” Objects. Galaxies 2018, 6, 131.

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