Anomalous abundance of lithium in the roAp star HD 12098 recently discovered in the northern hemisphere of the sky |
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Authors: | A V Shavrina N S Polosukhina N A Drake D O Kudryavtsev |
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Institution: | (1) Main Astronomical Observatory, National Academy of Sciences of Ukraine, Kiev, Ukraine;(2) Scientific Research Institute Crimean Astrophysical Observatory, Crimea, Ukraine;(3) Sobolev Institute of Astronomy, St. Petersburg State University, St. Petersburg, Russia;(4) Special Astronomical Observatory, Russian Academy of Sciences, Zelenchugskaya, Russia |
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Abstract: | Spectral observations of Ap-CP stars with the BTA (Special Astronomical Observatory, Russian Academy of Sciences) using the
NES echelle spectrometer have revealed several stars with an anomalous lithium abundance. The oscillating star HD 12098, which
is the first roAp star in the northern hemisphere of the sky, merits special attention. Strong, variable LiI 6708 Å line was
observed in the spectrum of this star. There are not enough observations for a reliable analysis by Doppler mapping, but there
are enough to indicate the presence of lithium spots on the surface of this star similar to the roAp stars HD 83368 and HD
60435, on whose surfaces spots with a high lithium abundance have been reliably detected. Parameters for a model of its atmosphere
have been chosen using the method of synthetic spectra based on atmospheric models including lines from the VALD list and
several additional blended REE lines calculated by the authors. The profile of the lithium LiI 6708 Å blend has been calculated
taking the magnetic field into account using the SYNTHM code. A lithium abundance has been determined for two phases of the
rotation of HD 12098 that is anomalously high compared to the solar and meteoritic abundances. The large difference in the
lithium abundance in the two phases (in two different regions on the star's surface) exceeds 0.5 dex and is very close to
that which we have found by analyzing the spectra of the roAp stars HD 83368 and HD 60435. Thus, we have discovered yet another
roAp star, HD 12098, with lithium spots on its surface.
Translated from Astrofizika, Vol. 51, No. 4, pp. 607–616 (November 2008). |
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Keywords: | stars lithium abundance — individual HD 2098 |
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