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Issue A&A
Volume 428, Number 1, December II 2004
Page(s) 121 - 129
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:200400059



A&A 428, 121-129 (2004)
DOI: 10.1051/0004-6361:200400059

A search for very young Planetary Nebulae

G. Umana1, L. Cerrigone2, C. Trigilio1 and R. A. Zappalà2

1  Istituto di Radioastronomia del CNR, Stazione VLBI di Noto, CP 141 Noto, Italy
    e-mail: g.umana@ira.cnr.it
2  Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia 78, 95123 Catania, Italy

(Received 8 April 2003 / Accepted 23 July 2004)

Abstract
Despite numerous efforts, the transition from Asymptotic Giant Branch (AGB) stars to Planetary Nebulae (PN) is a poorly understood phase of stellar evolution. We have therefore carried out interferometric (VLA) radio observations of a sample of hot post-AGB stars, selected on the basis of their optical and infrared properties. Ten sources out of the 16 observed were detected. This indicates that most of our targets are surrounded by a nebula where the ionization has already started. This definitively determines the evolutionary status of the selected sources and provides us with a unique sample of very young Planetary Nebulae (yPNe). A comparison with another sample of yPNe confirms our working hypothesis that our targets are indeed very young, probably just in the transition toward PN. Finding transition objects is extremely important as they can provide unique clues for a better understanding of this important phase of stellar evolution.


Key words: stars: AGB and post-AGB -- planetary nebulae: general -- radio continuum: stars

SIMBAD Objects



© ESO 2004


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