Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001apj...558..730r&link_type=abstract
The Astrophysical Journal, Volume 558, Issue 2, pp. 730-738.
Astronomy and Astrophysics
Astronomy
4
Ism: Dust, Extinction, Interplanetary Medium, Galaxy: Solar Neighborhood, Stars: Abundances, Stars: Chromospheres, Stars: Evolution
Scientific paper
Accretion of interstellar dust material onto stellar atmospheres could be responsible for the lack of low-metallicity G dwarfs observed in the disk of our Galaxy, known as the G dwarf problem. This interpretation of the G dwarf problem would be consistent with a peaked distribution of G dwarf metallicities and reconcile the observations of both a well-mixed interstellar gas and a large scatter in the age-metallicity relation. The absence of G dwarf problem in the Galactic halo could also be easily explained by the lower density of dust grains and the higher velocity of the stars in the halo. In order to test this idea of atmospheric pollution by interstellar dust material, the Sun accretion rate of interstellar dust (ISD) iron is estimated, making use of in situ measurements at AU distances from the Sun and taking into account the solar gravitational and radiation pressure forces to describe the grains dynamics closer to the Sun. The dust grains do not actually reach the Sun surface, but their iron content does after their sublimation at a few solar radii. The flux of ISD measured by Ulysses and Galileo results in an iron accretion rate of the order of 10-20 Msolar yr-1 the flux of very large ISD recently measured with AMOR gives an accretion rate several orders of magnitude higher, 10-17 Msolar yr-1 being a probable value. For a G dwarf of real metallicity [Fe/H]r, the metallicity of the stellar atmosphere (the observed one) will therefore differ from the metallicity [Fe/H]r of the stellar interior if the dilution of the accreted iron into the interior of the star happens on a timescale longer than 1-100×10[Fe/H]r+3 yr. Further studies of the particle transport between the atmosphere and convection zone will be needed to conclude about the plausibility of these values.
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