The frequency ratio method and the new multiperiodic gamma Doradus star HD 218427
English
Rodríguez, E.[Instituto de Astrofísica de Andalucía, CSIC, PO Box 3004, 18080 Granada, Spain]
Amado, P. J.[Instituto de Astrofísica de Andalucía, CSIC, PO Box 3004, 18080 Granada, Spain; European Southern Observatory, Alonso de Cordova 3107, Santiago 19, Chile]
Suárez, J. C.[Instituto de Astrofísica de Andalucía, CSIC, PO Box 3004, 18080 Granada, Spain; LESIA, Observatoire de Paris-Meudon, UMR 8109, 92190 Meudon, France]
Moya, A.[Instituto de Astrofísica de Andalucía, CSIC, PO Box 3004, 18080 Granada, Spain; LESIA, Observatoire de Paris-Meudon, UMR 8109, 92190 Meudon, France]
Dupret, Marc-Antoine[Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique >]
Poretti, E.[INAF-Osservatorio Astronomico di Brera, via E. Bianchi 46, 23807 Merate, Italy]
Grigahcène, A.[CRAAG, Algiers Observatory, BP 63 Bouzareah, 16340 Algiers, Algeria]
Costa, V.[Instituto de Astrofísica de Andalucía, CSIC, PO Box 3004, 18080 Granada, Spain]
López-González, M. J.[Instituto de Astrofísica de Andalucía, CSIC, PO Box 3004, 18080 Granada, Spain]
[en] stars: variables: general ; stars: individual: HD 218427 ; stars: oscillations ; techniques: photometric
[en] Oscillations of gamma Dor-type were discovered in the star HD 218427 through simultaneous uvby photometric observations carried out in the year 2003. A few Hbeta-Crawford measurements were also collected for calibration purposes and they locate this star well inside the gamma Dor instability region. We find HD 218427 to be deficient in metals, similar to other well-defined gamma Dor stars, and discuss the possibility that it has a lambda Boo nature. We carried out frequency analysis for different filters, including the combined "vby" filter, and five frequencies were found as significant with periods ranging between 0.3 and 0.8 days. The recently-developed frequency ratio method is used in order to identify the excited modes. The results are consistent with an l=2 identification for all the modes and with high radial quantum numbers (nË 40) for the three main observed periodicities. The possibility of multiplet structures is also discussed. However, no consistency is found when using the time-dependent convection treatment to discriminate modes. This disagreement can be due to the large rotation velocity taking place in HD 218427 and, consequently, the significant coupling between the modes.
