Fundamental parameters of bright Ap stars from wide-range energy distributions and advanced atmospheric models

¹ Institute of Astrophysics, Georg-August University, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
e-mail: denis.shulyak@gmail.com
² Institute of Astronomy, Russian Academy of Science, Pyatnitskaya 48, 119017 Moscow, Russia
³ Universität Wien, Institut für Astronomie, Türkenschanzstraße 17, 1180 Wien, Austria
⁴ Department of Physics and Astronomy, Uppsala University, PO Box 516, 751 20 Uppsala, Sweden

Received: 21 September 2012
Accepted: 8 November 2012

Abstract

Aims. As a well-established procedure for the vast majority of normal main-sequence stars, determination of atmospheric and stellar parameters turns to be a challenging process in case of magnetic chemically peculiar stars. Inhomogeneous distribution of chemical elements and strong magnetic fields make most of the standard photometric and spectroscopic calibrations inapplicable for this class of stars. In this work we make use of available observed energy distributions calibrated to absolute units, stellar parallaxes, high-resolution spectroscopic observations, and advanced stellar atmosphere models to derive parameters of three bright Ap stars: 33 Lib, γ Equ, and β CrB.

Methods. Model atmospheres and fluxes were computed with the LLmodels code. Synth3 and Synthmag codes were used to compute profiles of individual spectral lines involved in abundance analysis.

Results. For each of the stars, we construct a self-consistent atmospheric models assuming normal and depleted helium compositions and derive empirically stratification profiles of certain elements. The effective temperatures and surface gravities are found from the simultaneous fit to spectroscopic, photometric, and spectrophotometric observations calibrated to absolute units. We show that using advanced model atmospheres and accurate stellar parallaxes allows one to derive stellar radii with high accuracy, and these are consistent with those obtained from independent but more complicated interferometric observations.