Summary: Astronomy & Astrophysics manuscript no. 7834 c ESO 2008
February 1, 2008
Isotopic anomaly and stratification of Ca in magnetic Ap stars
T. Ryabchikova1,2, O. Kochukhov3, and S. Bagnulo4
Department of Astronomy, University of Vienna, T¨urkenschanzstraße 17, 1180 Vienna, Austria
Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya 48, 109017 Moscow, Russia
Department of Physics and Astronomy, Uppsala University, SE-751 20, Uppsala, Sweden
Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland
Received / Accepted
Aims. We have carried out an accurate investigation of the Ca isotopic composition and stratification in the atmospheres of 23
magnetic chemically peculiar (Ap) stars of different temperature and magnetic field strength.
Methods. With the UVES spectrograph at the 8 m ESO VLT, we have obtained high-resolution spectra of Ap stars in the wavelength
range 300010000 Å. Using a detailed spectrum synthesis calculations, we have reproduced a variety of Ca lines in the optical and
ultraviolet spectral regions, inferring the overall vertical distribution of Ca abundance, then we have deduced the relative isotopic
composition and its dependence on height using the profile of the the IR-triplet Ca II line at 8498 Å.