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Centro de Astrofísica da Universidade do Porto

Discovery of the longest-period rapidly oscillating Ap star HD177765

D. Alentiev, O. Kochukhov, T. Ryabchikova, M. S. Cunha, V. Tsymbal, W. W. Weiss

Abstract
We present the discovery of a long-period, rapidly oscillating Ap star, HD177765. Using high-resolution time-series observations obtained with UVES at the ESO VLT telescope, we found radial velocity variations with amplitudes 7–150 ms-1 and a period of 23.6 min, exceeding that of any previously known roAp star. The largest pulsation amplitudes are observed for Eu III, Ce III and for the narrow core of Hα. We derived the atmospheric parameters and chemical composition of HD177765, showing this star to be similar to other long-period roAp stars. Comparison with theoretical pulsational models indicates an advanced evolutionary state for HD177765. Abundance analyses of this and other roAp stars suggest a systematic variation with age of the rare-earth line anomalies seen in cool Ap stars.

Keywords
stars: chemically peculiar – stars: individual: HD177765 – stars: magnetic field – stars: oscillations

Notes
Based on observations collected at the European Southern Observatory, Paranal, Chile (program 085.D-0124).

Monthly Notices of the Royal Astronomical Society
Volume 421, Page L82
March 2012

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