2017A&A...602A..13C


Query : 2017A&A...602A..13C

2017A&A...602A..13C - Astronomy and Astrophysics, volume 602A, 13-13 (2017/6-1)

Evolution of long-lived globular cluster stars. IV. Initial helium content and white-dwarf properties.

CHANTEREAU W., CHARBONNEL C. and MEYNET G.

Abstract (from CDS):

Context. Globular clusters host stars with chemical peculiarities. The associated helium enrichment is expected to affect the evolution of stars, in general, and of low-mass stars, and in particular the progenitors of white dwarfs (WDs).
Aims. We investigate the effects of different initial helium contents on the properties of WDs such as their masses, compositions, and the time since their formation.
Methods. We used the grid of stellar models that we presented in the first papers of this series, which were computed for low-mass, low-metallicity stars with different helium content at [Fe/H]=-1.75 up to the end of the thermally pulsing asymptotic giant branch (TP-AGB) phase. We determined an initial-to-final mass relation as a function of the initial helium mass fraction, where the final mass is determined at the end of the TP-AGB phase. We couple the results with different possible distributions of the initial helium content for low-mass stars in NGC 6752 to predict the properties of WDs in this cluster.
Results. In a globular cluster at a given age, the He enrichment implies lower initial masses for stars at a given phase. Thus it leads to a decrease of the masses of WDs reaching the cooling sequence. In addition the He enrichment increases the total mass and number of WDs and eventually allows the presence of He white dwarf from single progenitors.
Conclusions. The low He enrichment determined in most globular clusters with different methods results in negligible effects on the white dwarf properties. However, in the few globular clusters that display a high He enrichment, this may significantly affect the characteristics of the WDs. In NGC 2808 and ω Centauri the high He enrichment even leads to the formation of He WDs from single He-rich progenitors. Therefore investigating the white dwarf mass domain in globular clusters with a high He enrichment would provide an additional indirect way to measure and constrain the He enrichment degree.

Abstract Copyright: © ESO, 2017

Journal keyword(s): stars: abundances - white dwarfs - stars: chemically peculiar - stars: evolution - stars: low-mass - globular clusters: general - globular clusters: general

Simbad objects: 10

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Number of rows : 10
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 NGC 2419 GlC 07 38 08.51 +38 52 54.9     10.05     ~ 884 0
2 NGC 2808 GlC 09 12 03.10 -64 51 48.6           ~ 1345 0
3 NGC 5139 GlC 13 26 47.28 -47 28 46.1   6.12 5.33     ~ 3264 0
4 M 4 GlC 16 23 35.22 -26 31 32.7           ~ 1771 0
5 M 62 GlC 17 01 12.60 -30 06 44.5   8.55 7.39     ~ 569 0
6 NGC 6388 GlC 17 36 17.461 -44 44 08.34   7.40       ~ 867 1
7 NGC 6441 GlC 17 50 13.06 -37 03 05.2   9.26 8.00     ~ 834 0
8 NGC 6752 GlC 19 10 52.11 -59 59 04.4   6.96 6.28     ~ 1910 0
9 NGC 6791 OpC 19 20 53 +37 46.7   10.52 9.5     ~ 971 0
10 M 2 GlC 21 33 27.02 -00 49 23.7     6.25     ~ 972 1

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2022.09.26-18:59:18

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