Abundance analysis and searching for nonradial pulsations in the atmosphere of the chemically peculiar star HD 115708 |
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| Authors: | E A Semenko M E Sachkov T A Ryabchikova D O Kudryavtsev N E Piskunov |
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| Institution: | (1) Special Astrophysical Observatory, Russian Academy of Sciences, Nizhnii Arkhyz, 357147, Karachai-Cherkessian Republic, Russia;(2) Institute of Astronomy, Russian Academy of Sciences, ul. Pyatnitskaya 48, Moscow, 119017, Russia;(3) Uppsala University, Uppsala, Sweden |
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| Abstract: | We present the results of our abundance analysis for the magnetic chemically peculiar star HD 115708 based on high-resolution spectra. The atmospheric chemical composition of HD 115708 (T eff = 7550 K) is shown to be typical of cool Ap stars with a significant ionization disequilibrium for the first and second rare earth ions, which is commonly observed in the atmospheres of pulsating Ap (roAp) stars. Our study of the vertical distribution of elements has shown that Mg, Ca, Cr, and Fe concentrate in deeper atmospheric layers, with their abundances decreasing sharply in the upper layers. The jumps in abundance are 1.5–3 orders of magnitude. Silicon is distributed in depth almost uniformly in the atmosphere of HD 115708. The derived empirical Cr and Fe distributions agree qualitatively with the results of diffusion calculations. Since the atmospheric chemical peculiarities in HD 115708 correspond to roAp stars, we have performed a spectroscopic monitoring to find nonradial pulsations. We have been able to determine only an upper limit for the amplitude of the possible radial velocity pulsations, ～100 m s?1, due to the insufficient temporal resolution and instability of the main stellar spectrograph (MSS) of the 6-m telescope. |
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| Keywords: | stars— properties and classification chemically peculiar stars magnetic field chemical composition roAp stars |
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