Structural Properties of s - Cepheid Velocity Curves ⋆
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چکیده
The light curves of the first overtone Pop. I Cepheids (s-Cepheids) show a discontinuity in their φ 21 vs. P diagram, near P = 3.2 day. This feature, commonly attributed to the 2:1 resonance between the first and the fourth overtones (ω 4 ≈ 2ω 1), is not reproduced by the hydrodynamical models. With the goal of reexamining the resonance hypothesis, we have obtained new CORAVEL radial velocity curves for 14 overtone Cepheids. Together with 10 objects of Krzyt et al. (1999), the combined sample covers the whole range of overtone Cepheid periods. The velocity Fourier parameters display a strong characteristic resonant behavior. In striking contrast to photometric ones, they vary smoothly with the pulsation period and show no jump at 3.2 day. The existing radiative hydrodynamical models match the velocity parameters very well. The center of the ω 4 = 2ω 1 resonance is estimated to occur at P r = 4.58 ± 0.04 day, i.e. at a period considerably longer than previously assumed (3.2 day). We identify two new members of the s-Cepheid group: MY Pup and V440 Per.
منابع مشابه
ASTRONOMY AND ASTROPHYSICS Structural Properties of s-Cepheid Velocity Curves ⋆ Constraining the location of the ω4 = 2ω1 resonance
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تاریخ انتشار 1998