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Astron. Astrophys. 348, 175-183 (1999)


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A slope variation in the period-luminosity relation for short period SMC Cepheids *

The EROS collaboration F. Bauer 1,2, C. Afonso 2, J.N. Albert 3, C. Alard 4, J. Andersen 5, R. Ansari 3, É. Aubourg 2, P. Bareyre 1,2, J.P. Beaulieu 4,12, A. Bouquet 1, S. Char[FORMULA]  6, X. Charlot 2, F. Couchot 3, C. Coutures 2, F. Derue 3, R. Ferlet 4, C. Gaucherel 2, J.F. Glicenstein 2, B. Goldman 2,7,8, A. Gould **  9, D. Graff 2,10, M. Gros 2, J. Haissinski 3, J.C. Hamilton 1, D. Hardin 2, J. de Kat 2, A. Kim 1, T. Lasserre 2, É. Lesquoy 2, C. Loup 4, C. Magneville 2, B. Mansoux 3, J.B. Marquette 4, É. Maurice 11, A. Milsztajn 2, M. Moniez 3, N. Palanque-Delabrouille 2, O. Perdereau 3, L. Prévot 11, C. Renault 2, N. Regnault 3, J. Rich 2, M. Spiro 2, A. Vidal-Madjar 4, L. Vigroux 2 and S. Zylberajch 2

1 Collège de France, PCC, IN2P3 CNRS, 11 place Marcelin Berthelot, F-75231 Paris Cedex, France
2 CEA, DSM, DAPNIA, Centre d'Études de Saclay, F-91191 Gif-sur-Yvette, Cedex, France
3 Laboratoire de l'Accélérateur Linéaire, IN2P3 CNRS et Université Paris-Sud, B.P. 34, F-91898 Orsay Cedex, France
4 Institut d'Astrophysique de Paris, INSU CNRS, 98 bis Boulevard Arago, F-75014 Paris, France
5 Astronomical Observatory, Copenhagen University, Juliane Maries Vej 30, DK-2100 Copenhagen, Denmark
6 Universidad de la Serena, Facultad de Ciencias, Departamento de Fisica, Casilla 554, La Serena, Chile
7 Department Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
8 European Southern Observatory, Casilla 19001, Santiago 19, Chile
9 Department of Astronomy, Ohio State University, Columbus, OH 43210, USA
10 Physics Department, Ohio State University, Columbus, OH 43210, USA
11 Observatoire de Marseille, 2 place Le Verrier, F-13248 Marseille Cedex 04, France
12 Kapteyn Laboratorium, Postbus 800, 9700 AD Groningen, The Netherlands

Received 15 July 1998 / Accepted 4 June 1999

Abstract

We present the Period-Luminosity relations from 290 Cepheids towards the LMC and 590 Cepheids towards the SMC. The two data sets were obtained using the two wide field CCD cameras of the EROS 2 microlensing survey. We observe a significant slope change of the period-luminosity relation for the SMC fundamental mode Cepheids with periods shorter than 2 days. Many possible experimental biases have been investigated, but none can account for this effect. We also observe different spatial distributions for SMC Cepheids with different ages i.e. periods. Different possible explanations of the slope change are discussed.

Key words: surveys – stars: variables: Cepheids – galaxies: Magellanic Clouds

* Based on observations made at ESO, La Silla, Chile.
** Alfred P. Sloan Foundation Fellow

Send offprint requests to: Florian.Bauer@cea.fr

© European Southern Observatory (ESO) 1999

Online publication: July 16, 1999

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