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Astron. Astrophys. 321, 145-150 (1997)
Amplitude monitoring of the ![[FORMULA]](img1.gif)
Cephei star 16 Lacertae
J.P. Sareyan 1,
J. Chauville 2,
E. Chapellier 1 and
M. Alvarez 3
1 Observatoire de la Côte d'Azur, Dept. Fresnel,
B.P.229, F-06003 Nice Cedex, France
2 Observatoire de Meudon, URA 335 du CNRS, F-92195 Meudon
Cedex, France
3 Observatorio Astronomico Nacional, UNAM, Apdo 877,
Ensenada, B.C. 22800, Mexico
Received 20 September 1995 / Accepted 5 March 1996
Abstract
Based on new observations, it is shown here that the amplitude of
one of the three well known and stable short periods in the
Cep variable 16 Lac has changed: while the
radial mode ![[FORMULA]](img2.gif)
= 0.16917 d is near its lower
amplitude level and the amplitude variation of the non-radial mode
![[FORMULA]](img3.gif)
= 0.18173 d is still probably in phase with the
orbital period, the amplitude of the NR mode ![[FORMULA]](img4.gif)
=
0.17077 d has increased progressively by a factor two in the last ten
years. The observed phase of shows that at least
for this period, the previous ephemeris is no longer valid. Various
hypotheses are proposed to account for the observed amplitudes
variations.
Key words: stars: 16
Lac 
stars: variable
stars: binaries:
close
stars: oscillations
Send offprint requests to: J.P.Sareyan
Contents
- 1. Introduction
- 2. Observations
- 3. Analysis
- 4. Amplitudes
- 5. Other periods?
- 6. Light amplitudes
- 7. Phases of the different periods
- 8. About energy transfer
- 9. Looking for explanations
- 10. Conclusion
- Acknowledgements
- References
© European Southern Observatory (ESO) 1997
Online publication: June 30, 1998
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