The remarkably unremarkable global abundance variations of the magnetic Bp star HD 133652⋆
1 Max Planck Insitut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
2 Armagh Observatory, College Hill, Armagh, BT61 9DG, Northern Ireland, UK
3 Department of Physics and Astronomy, University of Western Ontario, London, Ontario, N6A 3K7, Canada
Received: 11 March 2015
Accepted: 8 June 2015
Context. In recent years, significant effort has been made to understand how the magnetic field strengths and atmospheric chemical abundances of Ap/Bp stars evolve during their main sequence lifetime by identifying a large number of Ap/Bp stars with accurately known ages. As a next step, these stars should be studied individually and in detail to offer further insight into the physics of how such main sequence stars evolve.
Aims. We have obtained high resolution spectra using the ESPaDOnS spectropolarimeter and FEROS spectrograph of the chemically peculiar, magnetic Bp star HD 133652. Using these data, we present a simple magnetic field model and abundance determinations of He, O, Mg, Si, Ti, Cr, Fe, Pr, and Nd.
Methods. Abundance analysis was performed using zeeman.f, a spectral synthesis program that includes the effects of magnetic fields on line formation. The magnetic field structure is approximated as a simple, co-linear multipole expansion that reproduces the observed variations of the line-of-sight magnetic field with phase. The abundance distribution of each element was modelled using a uniform abundance in each of the two magnetic hemispheres.
Results. Using the new magnetic field measurements, we were able to refine the rotation period of HD 133652 to P = 2.30405 ± 0.00002 d. The abundance analysis reveals that the elements modelled (except He, O and Mg) are overabundant compared to the Sun; however most elements studied do not show substantial differences in the large-scale mean abundances between the two magnetic hemispheres. The individual line profiles are very complex and clearly indicate the presence of significant small-scale abundance variations on the stellar surface.
Conclusions. These data are adequate to perform a useful investigation of the magnetic field structure and abundance distribution over the stellar surface. HD 133652 is now one of a growing list of hotter Bp stars of known age for which this type of analysis has been performed.
Key words: stars: abundances / stars: chemically peculiar / stars: magnetic field
Based in part on our own observations made with the European Southern Observatory (ESO) telescopes under the ESO programme 086.D-0449(A). It is also based in part on observations carried out at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Science de l’Universe of the Centre National de la Recherche Scientifique of France and the University of Hawaii.
© ESO, 2015