[en] We perform for the first time spectroscopic mode identification in the eclipsing binary beta Cephei star EN (16) Lac. This mode identification is based upon a time series of 942 line profiles of the He I lambda lambda 6678 Åline in its spectrum. All three known frequencies f[SUB]1[/SUB], f,SUB>2,/SUB>, f[SUB]3[/SUB] of the star are present in the line-profile variations, but we failed to find additional modes. Using different identification methods we find conclusive evidence for the radial nature of the main mode and for the l=2, m=0 identification of the mode with frequency f[SUB]2[/SUB]. A unique identification of the third mode is not possible from the spectra, but we do derive that l[SUB]3[/SUB]<3. Fits to the amplitude and phase variability of the modes imply a rotation frequency between 0.1 and 0.4 c d[SUP]-1[/SUP]. The star's rotation axis is not aligned with the orbital axis. Based on observations gathered with the coudé spectrograph attached to the 2.0 m reflector telescope at Tautenburg Observatory.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Aerts, C.; Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200 B, 3001 Leuven, Belgium
Briquet, Maryline ; Institut d'Astrophysique et de Géophysique de Liège, Université de Liège, allée du Six Août 17, 4000 Liège, Belgium
Scuflaire, Richard ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Evol. et stabilité des étoiles et des amas d'étoiles (ESEA)
Dupret, Marc-Antoine ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique
De Ridder, J.; Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200 B, 3001 Leuven, Belgium
Thoul, Anne ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Evol. et stabilité des étoiles et des amas d'étoiles (ESEA)
Language :
English
Title :
Spectroscopic mode identification for the beta Cephei star EN (16) Lacertae
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