Lithium and the 6Li-7Li isotope ratio in the atmospheres of some sharp-lined roAp stars |
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| Authors: | A V Shavrina N S Polosukhina S Khan Ya V Pavlenko D O Kudryavtsev V R Khalack N G Mikha?litskaya Yu P Lyubchik A V Yushchenko A Hatzes D E Mkrtichian I V Il’in |
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| Institution: | (1) Main Astronomical Observatory, ul. Akademika Zabolotnogo 27, Kiev, 03680, Ukraine;(2) Crimean Astrophysical Observatory, Nauchnyĭ, Crimea, 98409, Ukraine;(3) Physics and Astronomy Department, University of Western Ontario, 1151 Richmond Str., London, ON, N6A 3K7, Canada;(4) Special Astrophysical Observatory, Russian Academy of Sciences, Nizhnii Arkhyz, Karachai-Cherkessian Republic, 357147, Russia;(5) Département de Physique et d’Astronomie, Université de Moncton, Moncton, N.-B., E1A 3E9, Canada;(6) Astrophysical Research Center for the Structure and Evolution of the Cosmos, Sejong University, Seoul, 143-747, Korea;(7) Odessa Astronomical Observatory, Mechnikov National University, Shevchenko Park, Odessa, 65014, Ukraine;(8) Thüringer Landessternwarte Tautenburg, Karl-Schwarzschild-Observatorium, Sternwarte 5, Tautenburg, D-07778, Germany;(9) Astrophysikalisches Institut Potsdam, An der Sternwarte 16, Potsdam, D-14482, Germany |
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| Abstract: | The λ 6708 Å and 6103 Å lithium lines in the high-resolution spectra of some sharp-lined roAp stars are analyzed using three spectral-synthesis codes STARSP, ZEEMAN2, and SYNTHM. The lines from the VALD database were supplemented with lines of rare-earth elements from the DREAM database and new lines calculated using the NIST energy levels. Our synthetic-spectrum calculations take into account magnetic splitting and other line-broadening effects. Lithium overabundances were found in the atmospheres of the stars based on our analysis of both lithium lines, along with high values of the 6Li-7Li isotope ratio (0.2–0.5). This can be explained if lithium is produced in spallation reactions and the surface 6Li and 7Li is preserved by strong magnetic fields in the upper layers of the stellar atmospheres, around the poles of the dipole field. The asymmetry of lithium lines to the red may be due to the action of shocks in the optically thin upper atmosphere, with the shocked material subsequently falling onto the star. |
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