Abundances in the Herbig Ae star HD 101412

Abundance anomalies; λ Boo–Vega characteristics?^⋆

¹ Department of Astronomy, University of Michigan, Ann Arbor, MI 48109-1090, USA
e-mail: cowley@umich.edu
² AIP, An der Sternwarte 16, 14482 Potsdam, Germany
e-mail: shubrig@aip.de
³ Instituto de Ciencias Astronómicas, del la Terra y del Espacio, Casilla 467, 5400 San Juan, Argentina
e-mail: fgonzalez@icate-conicet.gob.ar
⁴ Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya 48, Moscow 119017, Russia
e-mail: isavenov@rambler.ru

Received: 7 July 2010
Accepted: 9 August 2010

Abstract

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 mÅ) 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 λ 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.