W. J. Maciel -
Abstract #123
AGES OF CENTRAL STARS OF PLANETARY NEBULAE
W. J. Maciel, R. D. D. Costa, T. E. P. Idiart,
IAU Symposium 258, The Ages of Stars,
CUP, ed. E.E. Mamajek, D.R. Soderblom, R.F.G. Wyse (2009),
(electronic publication, http://abstracts.stsci.edu/IAU258/Maciel.pdf),
The determination of ages of central stars of planetary nebulae (CSPN) is a complex
problem, and there is presently no single method that can be generally applied.
Our group has pioneered in the treatment of this problem, and we have developed
several methods to estimate the ages of the PN progenitor stars, based both on
the observed nebular properties and in some properties of the stars themselves.
In principle, the traditional methods to derive the ages of galactic stars can be
applied to CSPN, such as the use of theoretical isochrones. However, the physical
properties of these objects are not as well known as in the case of normal stars,
so that the derived isochrones are generally uncertain, leading to the need of
alternative methods. In this work, we will discuss several methods developed so
far by our group, such as (i) the use of an age-metallicity relation that also
depends on the galactocentric radius, (ii) the determination of ages from the
central star masses obtained from the observed nitrogen abundances, and (iii) the
use of an age-metallicity relation obtained for the galactic disk. Also, theoretical
isochrones for AGB stars have been used to derive ages of CSPN in the SMC. We estimate
the expected age distribution of the CSPN based on the observed distribution of white
dwarf stars, and compare the results with the distributions obtained by the methods
mentioned above and with available mass distributions of CSPN.
