Query : 1997A&A...321..485U

1997A&A...321..485U - Astronomy and Astrophysics, volume 321, 485-491 (1997/5-2)

The influence of gravitational settling and selective radiative forces in PG 1159 stars. II.


Abstract (from CDS):

Previous investigations have shown that time-independent diffusion calculations cannot explain the large abundances of carbon and oxygen in the helium-dominated atmospheres of hot pre-white dwarfs. Therefore we investigate in this paper the time evolution of the chemical composition in the outer regions with surface layer masses ≤10–8M*. The elements He, C, N, O and Ne are taken into account. It is shown that for logg=7.0 and Teff=140000K and 65000K, respectively, gravitational settling should lead to a strong depletion of both elements within a time-scale of 1000y. According to theoretical evolutionary tracks for post-AGB stars, PG 1159 stars with M*∼0.6M should have passed through regions in the HRD with Teff=140000K and logg∼6.0. For these model parameters the radiative forces are strong enough to transform a helium-rich atmosphere with only traces of heavy elements into a metal-rich one. However, this transformation takes about 800000y, long compared to the corresponding time-scales of stellar evolution. For more massive objects, the observational results cannot be explained by diffusion processes alone.

Abstract Copyright:

Journal keyword(s): stars: abundances - stars: evolution - diffusion - white dwarfs

Simbad objects: 3

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Number of rows : 3
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
1 V* GW Vir WD* 12 01 45.9731868264 -03 45 40.628670300   14.87 15.04     DOQZ1 475 0
2 PG 1501+664 WD* 15 02 09.6299323152 +66 12 19.148868324   16.07 16.37     DZQ1 153 0
3 PG 1520+525 PN 15 21 46.5635130432 +52 22 03.867341340   15.56 16.6     PG1159 107 1

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