Volume 568, August 2014
|Number of page(s)||7|
|Published online||20 August 2014|
Atmospheric dynamics in long-period Cepheids
Hα profile variations
Observatoire de Haute-Provence – CNRS/PYTHEAS/Université d’Aix-Marseille, 04870 Saint Michel l’Observatoire, France
Received: 22 January 2014
Accepted: 13 June 2014
Context. Despite recent time series of very high quality of Hα profile variations of classical Cepheids, the dynamics of the pulsating atmosphere of long-period Cepheids is not yet understood.
Aims. Taking into account the propagation of intense shock waves in the atmosphere, we propose a general scheme of the atmospheric dynamics in long-period Cepheids.
Methods. We use a time series of Hα profiles of the long-period Cepheid X Cygni and HARPS high-resolution spectroscopy of three long-period Cepheids that have not yet been fully interpreted.
Results. Caused by the main shock occurring at each pulsation cycle, the Hα profile first presents a blueshifted component in emission or in absorption depending on the shock intensity. Then, when the shock is detached from the photosphere, the emission shifts on the red side of the line profile which now has the form of a P Cygni profile. A second shock is also observed. It is the consequence of the ballistic motion of the atmosphere. Thus, the interaction of the main shock with infalling layers can qualitatively explain observed variable peculiairities in the Hα profile.
Conclusions. The evolution of the Hα profile occurring in long-period Cepheids is similar to the evolution observed in radially pulsating stars such as RR Lyrae stars, in which the intensity of the main shock is strong enough to induce a propagation away from the photosphere.
Key words: stars: variables: Cepheids / stars: atmospheres / shock waves
© ESO, 2014
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.