Spectroscopy of the roAp star α Cir — I. Velocities of Hα and metal lines |
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| Authors: | I KBaldry T RBedding MViskum HKjeldsen SFrandsen |
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| Institution: | Chatterton Astronomy Department, School of Physics, University of Sydney, NSW 2006, Australia; Institute of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark; Theoretical Astrophysics Center, University of Aarhus, DK-8000 Aarhus C, Denmark |
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| Abstract: | We present radial velocity measurements of the rapidly oscillating Ap (roAp) star α Cir, obtained from dual-site observations with medium-dispersion spectrographs. The amplitude and phase of the principal pulsation mode vary significantly, depending on which line is being measured. The amplitude is observed to be as high as 1000 m s?1 in some wavelength bands, despite a previous upper limit of 36 m s?1. Furthermore, some lines are apparently pulsating in anti-phase with others. We suggest this indicates a high-overtone standing wave with a velocity node in the atmosphere of the star. |
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| Keywords: | techniques: radial velocities stars: chemically peculiar stars: individual: α Cir stars: oscillations |
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