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Chemical composition and evolutionary status of the Ap star HD 138633 |
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| Authors: | A P Titarenko T A Ryabchikova O P Kochukhov V V Tsymbal |
| Institution: | 19341. Department of Astronomy, Faculty of Physics, Moscow State University, Moscow, 119991, Russia 29341. Institute of Astronomy, Russian Academy of Sciences, ul. Pyatnitskaya 48, Moscow, 119017, Russia 39341. Department of Astronomy and Space Physics, Uppsala University, Box 515, 751-20, Uppsala, Sweden 49341. Faculty of Physics, Taurida National University, pr. Vernadskogo 4, Simferopol, 95007, Ukraine |
| Abstract: | We present the results of our study of the atmospheric chemical composition and evolutionary status for the chemically peculiar Ap star HD 138633. In contrast to ordinary Ap stars that exhibit strong lines of rare-earth elements in their spectra, these elements are represented very poorly in the spectrum of HD 138633. The magnetic field is estimated to be less than 700 G, which is also atypical of peculiar Ap stars. We have detected a stratification of such elements as Fe, Si, Ca, and Y in the atmosphere of HD 138633 whose pattern agrees qualitatively with the predictions of the theory of diffusive separation of elements under the joint action of gravity and radiation pressure forces. The nonuniform distribution obtained by assuming a stepwise distribution of elements in depth agrees qualitatively with the stratification distribution for β CrB. The search for pulsations points to the possible existence of lowamplitude pulsations with a period of about 17 min. |
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