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Abundances in the Herbig Ae star HD 101412: Abundance anomalies; Lambda Boo-Vega characteristics? | | C. R. Cowley
; S. Hubrig
; J. F. González
; I. Savanov
; | | Date: |
10 Aug 2010 | | Abstract: | Context: Recent attention has been directed to abundance variations among
very young stars.
Aims: To perform a detailed abundance study of the Herbig Ae star HD 101412,
taking advantage of its unusually sharp spectral lines.
Methods: High-resolution spectra are measured for accurate wavelengths and
equivalent widths. Balmer-line fits and ionization equlibria give a relation
between Teff, and log(g). Abundance anomalies and uncertain reddening preclude
the use of spectral type or photometry to fix Teff. Excitation temperatures are
used to break the degeneracy between Teff and log(g).
Results: Strong lines are subject to an anomalous saturation that cannot be
removed by assuming a low microturbulence. By restricting the analysis to weak
(<= 20 m[A]) lines, we find consistent results for neutral and ionized species,
based on a model with Teff = 8300K, and log(g)=3.8. The photosphere is depleted
in the most refractory elements, while volatiles are normal or, in the case of
nitrogen, overabundant with respect to the sun. The anomalies are unlike those
of Ap or Am stars.
Conclusions: We suggest the anomalous saturation of strong lines arises from
heating of the upper atmospheric layers by infalling material from a disk. The
overall abundance pattern may be related to those found for the Lambda Boo
stars, though the depletions of the refractory elements are milder, more like
those of Vega. However, the intermediate volatile zinc is depleted, precluding
a straightforward interpretation of the abundance pattern in terms of gas-grain
separation. | | Source: | arXiv, 1008.1601 | | Services: | Forum | Review | PDF | Favorites | |
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