Astron. Astrophys. 321, L5-L8 (1997)

Letter to the Editor

EROS VARIABLE STARS: Discovery of Beat Cepheids in the Small Magellanic Cloud
and the effect of metallicity on pulsation

J.P. Beaulieu ^{1, 2}, M. Krockenberger ³, D.D. Sasselov ³, C. Renault ⁴, R. Ferlet ¹, A. Vidal-Madjar ¹, E. Maurice ⁵, L. Prévot ⁵, E. Aubourg ⁴, P. Bareyre ⁴, S. Brehin ⁴, C. Coutures ⁴, N. Delabrouille ⁴, J. de Kat ⁴, M. Gros ⁴, B. Laurent ⁴, M. Lachièze-Rey ⁴, E. Lesquoy ⁴, C. Magneville ⁴, A. Milsztajn ⁴, L. Moscoso ⁴, F. Queinnec ⁴, J. Rich ⁴, M. Spiro ⁴, L. Vigroux ⁴, S. Zylberajch ⁴, R. Ansari ⁶, F. Cavalier ⁶, M. Moniez ⁶ and C. GryThe EROS Collaboration <sup>7

1</sup> Kapteyn Laboratorium, Postbus 800 9700 AV Groningen, The Netherlands
² Institut d'Astrophysique de Paris, CNRS, 98bis Boulevard. Arago, F-75014 Paris, France
³ Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA
⁴ CEA, DSM/DAPNIA, Centre d'études de Saclay, F-91191 Gif-sur-Yvette, France
⁵ Observatoire de Marseille, 2 place Le Verrier, F-13248 Marseille 04, France
⁶ Laboratoire de l'Accélérateur Linéaire IN2P3, Centre d'Orsay, F-91405 Orsay, France
⁷ Laboratoire d'Astronomie Spatiale CNRS, Traversée du siphon, les trois lucs, F-13120 Marseille, France

Received 10 January 1997 / Accepted 7 February 1997

Abstract

We report the discovery of eleven beat Cepheids in the Small Magellanic Cloud, using data obtained by the EROS microlensing survey. Four stars are beating in the fundamental and first overtone mode (F/1OT), seven are beating in the first and second overtone (1OT/2OT). The SMC F/1OT ratio is systematically higher than the LMC F/1OT, while the 1OT/2OT period ratio in the SMC Cepheids is the same as the LMC one.

Key words: stars : oscillations - stars cepheids - galaxies : Magellanic Clouds

Send offprint requests to: JP. Beaulieu, beaulieu@astro.rug.nl

SIMBAD Objects

Contents

• 1. Introduction
• 2. EROS Observations
• 3. Beat Cepheids
  • 3.1. Identification and Fourier decomposition
  • 3.2. Period ratios
• 4. Fourier coefficients
• 5. Conclusion
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998
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