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Astron. Astrophys. 343, 202-212 (1999)


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The RV Tauri phenomenon and binarity *

H. Van Winckel  **  1, C. Waelkens 1, J.D. Fernie 2 and L.B.F.M. Waters 3

1 Instituut voor Sterrenkunde, K.U. Leuven, Celestijnenlaan 200B, B-3001 Heverlee, Belgium
2 David Dunlap Observatory, University of Toronto, Box 360 Richmond Hill, Ontario, L4C 4Y6, Canada
3 Astronomical Institute "Anton Pannekoek", University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands

Received 21 September 1998 / Accepted 1 December 1998

Abstract

We present accurate radial velocity measurements on the pulsating extremely iron-deficient post-AGB object HD 52961 and the RV Tauri star EN TrA (HD 131356) proving them to be binaries. Our long-term photometric monitoring campaign shows that the RV Tauri photometric class "b" phenomenon in HD 52961 is due to variable circumstellar extinction during orbital motion.

By comparing carefully the observational characteristics of RV Tauri stars and the class of extremely iron-deficient post-AGB objects we conclude that binarity is a widespread phenomenon in the RV Tauri class of objects. The observed chemical depletion patterns, weak circumstellar CO emission, peculiar spectral energy distribution and the difference in photospheric class of the RV Tauri objects can all be naturally explained by assuming that the circumstellar material is not freely expanding, but trapped in the binary system.

Key words: stars: oscillations – stars: AGB and post-AGB – stars: individual: HD 52961, En TrA (HD 131356), HR 4049 – stars: evolution – stars: binaries: spectroscopic

* Based on observations collected at the European Southern Observatory (proposals codes 51.7-0052; 51.7-0053; 52.7-0048; 58.E-0462; 59.E-0432; 61.E-0426); with the Swiss telescopes at ESO and OHP and the APT telescope at Mt. Hopkins
** Postdoctoral fellow of the Fund for Scientific Research, Flanders

Send offprint requests to: H. Van Winckel (Hans.VanWinckel@ster.kuleuven.ac.be)

© European Southern Observatory (ESO) 1999

Online publication: March 1, 1999

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