The classification of frequencies in the γ Doradus / δ Scuti hybrid star HD 49434

Abstract

Hybrid stars of the γ Doradus and δ Scuti pulsation types have great potential for asteroseismic analysis to explore their interior structure. To achieve this, mode identi- fications of pulsational frequencies observed in the stars must be made, a task which is far from simple. In this work we begin the analysis by scrutinizing the frequencies found in the CoRoT photometric satellite measurements and ground-based high-resolution spectroscopy of the hybrid star HD 49434. The results show almost no consistency between the frequencies found using the two techniques and no characteristic period spacings or couplings were identified in either dataset. The spectroscopic data additionally show no evidence for any long term (5 year) variation in the dominant frequency. The 31 spectroscopic frequencies identified have standard deviation profiles suggesting multiple modes sharing (l, m) in the δ Scuti frequency region and several skewed modes sharing the same (l, m) in the γ Doradus frequency region. In addition, there is a clear frequency in the γ Doradus frequency region that appears to be unrelated to the others. We conclude HD 49434 remains a δ Scuti/ γ Doradus candidate hybrid star but more sophisticated models dealing with rotation are sought to obtain a clear picture of the pulsational behaviour of this star.

Accepted for publication in MNRAS December 2014

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• The Occurrence of Non-Pulsating Stars in the gamma Dor and delta Sct Pulsation Instability Regions: Results from Kepler Quarter 14-17 Data
• Hybrid Pulsators -- Pulsating Stars with Multiple Identities