Abundances in the Herbig Ae star HD 101412 Abundance anomalies; lambda Boo-Vega characteristics?

作者：Cowley C R^*; Hubrig S; Gonzalez J F; Savanov I

来源：Astronomy & Astrophysics, 2010, 523: A65.

DOI：10.1051/0004-6361/201015361

• stars: chemically peculiar
• stars: abundances
• stars: individual: HD 101412
• stars: pre-main sequence
• stars: early-type

Context. Recent attention has been directed to abundance variations among very young stars.
Aims. We 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 T-eff, and log(g). Abundance anomalies and uncertain reddening preclude the use of spectral type or photometry to fix T-eff. Excitation temperatures are used to break the degeneracy between T-eff 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 angstrom) lines, we find consistent results for neutral and ionized species, based on a model with T-eff = 8300 K, 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.

• 出版日期2010-12