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Astron. Astrophys. 344, L79-L82 (1999)

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Letter to the Editor

The hidden past of Sakurai's object

Stellar properties before the final helium flash

F. Kerber 1,2, J. Köppen 3,4,5, M. Roth 6 and S.C. Trager 6

1 Space Telescope European Coordinating Facility, European Southern Observatory, D-85748 Garching, Germany
2 Institut für Astronomie der Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
3 UMR 7550, Observatoire Astronomique, 11 Rue de l'Université, F-67000 Strasbourg, France
4 International Space University, Parc d'Innovation, F-67400 Illkirch, France
5 Institut für Theoretische Physik und Astrophysik der Universität, D-24098 Kiel, Germany
6 The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101, USA

Received 26 February 1999 / Accepted 18 March 1999


We derive the properties of Sakurai's object before its sudden evolutionary change by studying the remnant ionization of the old planetary nebula (PN) surrounding it. The star must have had a surface temperature of 98 000[FORMULA] K (95 000[FORMULA] K). For a distance of 1.5 kpc (5.5 kpc) the luminosity should have been 25 [FORMULA] 5 [FORMULA] (240 [FORMULA] 40 [FORMULA]). The central star thus was highly evolved and had already reached the tip of the white dwarf cooling track. Sakurai's object indeed is an example of a star undergoing a very late helium flash.

Key words: stars: AGB and post-AGB – stars: evolution – stars: Hertzsprung – Russel (HR) and C-M diagrams – ISM: planetary nebulae: individual: Sakurai's object – stars: variables: general

Send offprint requests to: F. Kerber (fkerber@eso.org)

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© European Southern Observatory (ESO) 1999

Online publication: March 29, 1999