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Astron. Astrophys. 351, 283-291 (1999)


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Lithium on the surface of cool magnetic CP stars *

I. Summary of spectroscopic observations with three telescopes

N. Polosukhina 1, D. Kurtz 2, M. Hack 3, P. North 4, I. Ilyin 5, J. Zverko 6 and D. Shakhovskoy 1

1 Crimean Astrophysical Observatory Nauchny, Crimea, Ukraine (polo@crao.crimea.ua)
2 University of Cape Town, Rondebosch 7700, South Africa (dkurtz@physci.uct.ac.za)
3 Department of Astronomy, Trieste University, Italy (hack@ts.astro.it)
4 Institut d'Astronomie de l'Université de Lausanne, 1290 Chavannes-des-Bois, Switzerland (pierre.north@obs.unige.ch)
5 University of Oulu, P.O. Box 3000, 90401 Oulu, Finland (Ilya.Ilyin@oulu.fi)
6 Astronomical Institute of the Slovak Academy of Sciences, 05960 Tatranská Lomnica, The Slovak Republic (zverko@ta3.sk)

Received 2 June 1999 / Accepted 1 July 1999

Abstract

We present new results of observations of the 6708 Å line in twelve CP stars made with three telescopes: the ESO CAT telescope, the Crimean Observatory (CrAO) 2.6-m telescope, and the Nordic Optical Telescope (NOT). Unique profile and wavelength variations of the line at 6708 Å were discovered in two stars, HD 60435 and HD 83368. We present arguments in favour of the identification of this feature with the resonant Li I line. According to the incidence and variability of this line, spectra of twelve stars were divided in four groups: Group 1 - the line is remarkably variable in intensity and wavelength; this group includes the stars HD 83386 and HD 60435; Group 2 - the line is variable to a lesser extent; includes [FORMULA] CrB and HD 188041; Group 3 - the line is not variable; includes 33 Lib, HD 134214, HD 166473 and [FORMULA] Equ; Group 4 - the line is not present; includes HD 42659, HD 80316, HD 118022 and HD 128898. The behaviour in Groups 1-3 can be explained by the existence of Li rich spots on the star's surface using the oblique rotator model with different inclination and magnetic obliquity for each star. For HD 83368 we have found a tight correlation between the visibility of the spots and the orientation of the dipole pulsation mode.

Key words: stars: chemically peculiar – stars: variables: general – stars: magnetic fields – stars: oscillations – line: identification – line: profiles

* Based on observations collected at the European Southern Observatory, La Silla, Chile, the Nordic Optical Telescope, La Palma, Spainand the Shajn Telescope, Crimean Astrophysical Observatory, Ukraine

Send offprint requests to: N. Polosukhina

© European Southern Observatory (ESO) 1999

Online publication: November 2, 1999

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