space vehicles: instruments; stars: variables: delta Scuti
Abstract :
[en] Observations of the pulsations of stars can be used to infer their interior structure and test theoretical models. The main-sequence γ Doradus (Dor) and δ Scuti (Sct) stars with masses 1.2-2.5 M [SUB]sun[/SUB] are particularly useful for these studies. The γ Dor stars pulsate in high-order g-modes with periods of order 1 day, driven by convective blocking at the base of their envelope convection zone. The δ Sct stars pulsate in low-order g- and p-modes with periods of order 2 hr, driven by the κ mechanism operating in the He II ionization zone. Theory predicts an overlap region in the Hertzsprung-Russell diagram between instability regions, where "hybrid" stars pulsating in both types of modes should exist. The two types of modes with properties governed by different portions of the stellar interior provide complementary model constraints. Among the known γ Dor and δ Sct stars, only four have been confirmed as hybrids. Now, analysis of combined Quarter 0 and Quarter 1 Kepler data for hundreds of variable stars shows that the frequency spectra are so rich that there are practically no pure δ Sct or γ Dor pulsators, i.e., essentially all of the stars show frequencies in both the δ Sct and the γ Dor frequency range. A new observational classification scheme is proposed that takes into account the amplitude as well as the frequency and is applied to categorize 234 stars as δ Sct, γ Dor, δ Sct/γ Dor or γ Dor/δ Sct hybrids.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Grigahcène, Ahmed
Antoci, V.; Institut fuer Astronomie, Tuerkenschanzstr. 17, A-1180 Wien, Austria
Balona, L.; South African Astronomical Observatory, P.O. Box 9, Observatory 7935, South Africa
Catanzaro, G.; INAF-Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy
Daszynska-Daszkiewicz, J.
Guzik, J. A.; Los Alamos National Laboratory, X-2 MS T-086, Los Alamos, NM 87545-2345, USA
Handler, G.; Institut fuer Astronomie, Tuerkenschanzstr. 17, A-1180 Wien, Austria
Houdek, G.; Institut fuer Astronomie, Tuerkenschanzstr. 17, A-1180 Wien, Austria
Kurtz, D. W.; Jeremiah Horrocks Institute of Astrophysics, University of Central Lancashire, Preston PR1Â 2HE, UK
Marconi, M.; INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Naples, Italy
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Ripepi, V.; INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Naples, Italy
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