C. Afonso

Galactic Bulge microlensing optical depth from EROS-2

We present a new EROS-2 measurement of the microlensing optical depth toward the Galactic Bulge. Light curves of

Type Ia supernova rate at a redshift of ~;0.1

5.6\times 10^{6}

New Magellanic Cloud R Coronae Borealis and DY Persei type stars from the EROS-2 database: the connection between RCBs, DYPers, and ordinary carbon stars

clump-giant stars distributed over

R Coronae Borealis stars in the Galactic Bulge discovered by EROS-2

66 \deg^2

Photometric constraints on microlens spectroscopy of EROS-BLG-2000-5

of the Bulge were monitored during seven Bulge seasons. 120 events were found with apparent amplifications greater than 1.6 and Einstein radius crossing times in the range

The EROS2 search for microlensing events towards the spiral arms: the complete seven season results

5 {\rm d}

Removing the Microlensing Blending-Parallax Degeneracy Using Source Variability

Astronomy & Astrophysics manuscript no. rate (DOI: will be inserted by hand later) May 12, 2004 Type Ia supernova rate at a redshift of ∼ 0.1 G. Blanc 1,12,22 , C. Afonso 1,4,8,23 , C. Alard 24 , J.N. Albert 2 , G. Aldering 15,28 , A. Amadon 1 , J. Andersen 6 , R. Ansari 2 , E. Aubourg 1 , C. Balland 13,21 , P. Bareyre 1,4 , J.P. Beaulieu 5 , X. Charlot 1 , A. Conley 15,28 , 1 , T. Dahl´ n 19 , F. Derue 13 , X. Fan 16 , R. Ferlet 5 , G. Folatelli 11 , P. Fouqu´ 9,10 , G. Garavini 11 , C. Coutures e e J.F. Glicenstein 1 , B. Goldman 1,4,8,23 , A. Goobar 11 , A. Gould 1,7 , D. Graff 7 , M. Gros 1 , J. Haissinski 2 , C. Hamadache 1 , D. Hardin 13 , I.M. Hook 25 , J. de Kat 1 , S. Kent 18 , A. Kim 15 , T. Lasserre 1 , L. Le Guillou 1 , E. Lesquoy 1,5 , C. Loup 5 , C. Magneville 1 , J.B. Marquette 5 , E. Maurice 3 , A. Maury 9 , A. Milsztajn 1 , M. Moniez 2 , M. Mouchet 20,22 , H. Newberg 17 , S. Nobili 11 , N. Palanque-Delabrouille 1 , O. Perdereau 2 , L. Pr´ vot 3 , Y.R. Rahal 2 , N. Regnault 2,14,15 , J. Rich 1 , P. Ruiz-Lapuente 27 , M. Spiro 1 , P. Tisserand 1 , e A. Vidal-Madjar 5 , L. Vigroux 1 , N.A. Walton 26 , S. Zylberajch 1 . arXiv:astro-ph/0405211 v1 11 May 2004 DSM/DAPNIA, CEA/Saclay, 91191 Gif-sur-Yvette Cedex, France Laboratoire de l’Acc´ l´ rateur Lin´ aire, IN2P3 CNRS, Universit´ Paris-Sud, 91405 Orsay Cedex, France e e e e Observatoire de Marseille, 2 pl. Le Verrier, 13248 Marseille Cedex 04, France Coll` ge de France, Physique Corpusculaire et Cosmologie, IN2P3 CNRS, 11 pl. M. Berthelot, 75231 Paris e Cedex, France Institut d’Astrophysique de Paris, INSU CNRS, 98 bis Boulevard Arago, 75014 Paris, France Astronomical Observatory, Copenhagen University, Juliane Maries Vej 30, 2100 Copenhagen, Denmark Departments of Astronomy and Physics, Ohio State University, Columbus, OH 43210, U.S.A. Department of Astronomy, New Mexico State University, Las Cruces, NM 88003-8001, U.S.A. European Southern Observatory (ESO), Casilla 19001, Santiago 19, Chile Observatoire Midi-Pyr´ n´ es, 14 avenue Edouard Belin, 31400 Toulouse, France e e Department of Physics, Stockholm University, AlbaNova University Center, S-106 91 Stockholm, Sweden Osservatorio Astronomico di Padova, INAF, vicolo dell’Osservatorio 5 - 35122 Padova, Italy Laboratoire de Physique Nucl´ aire et de Hautes Energies, IN2P3 - CNRS - Universit´ s Paris 6 et Paris 7, 4 e e place Jussieu, 75252 Paris Cedex 05, France Laboratoire Leprince-Ringuet, LLR/Ecole Polytechnique, Route de Saclay, 91128 Palaiseau CEDEX, France Lawrence Berkeley National Lab, 1 Cyclotron Road, Berkeley, CA 94720, U.S.A. Steward Observatory, The University of Arizona, 933 N. Cherry Ave, Tucson, AZ 85721-0065, U.S.A. Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, NY 12180, U.S.A. Fermilab Wilson and Kirk Roads, Batavia, IL 60510-0500, U.S.A. Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218, U.S.A. LUTH, Observatoire de Paris, 5, Place Jules Janssen, 92195 Meudon Cedex, France Institut d’Astrophysique Spatiale, Bˆ timent 121, Universit´ Paris 11, 91405 Orsay Cedex, France a e Universit´ Paris 7 Denis Diderot, 2, place Jussieu, 75005 Paris, France e NASA/Ames Research Center, Mail Stop 244, Moffet Field, CA 94035, U.S.A. GEPI, Observatoire de Paris, 77 avenue de l’Observatoire, 75014 Paris, France Department of Physics, University of Oxford, Nuclear and Astrophysics laboratory, Keble Road, Oxford OX1 3RH, UK Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK Department of Astronomy, University of Barcelona, Barcelona, Spain Visiting astronomer, Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatories, which are operated by the Association of Universities for Research in Astronomy, under contract with the National Science Foundation. Received / Accepted Abstract. We present the type Ia rate measurement based on two EROS supernova search campaigns (in 1999 and 2000). Sixteen supernovae identified as type Ia were discovered. The measurement of the detection efficiency, using a Monte Carlo simulation, provides the type Ia supernova explosion rate at a redshift ∼ 0.13. The result is 0.125 +0.044+0.028 h 2 SNu where 1 SNu = 1 SN / 10 10 L B / century. This value is compatible with the previous EROS measurement (Hardin et al. 2000), done with a much smaller sample, at a similar redshift. Comparison with other values at different redshifts suggests an evolution of the type Ia supernova rate. Key words. (Stars:) supernovae: general – Galaxies: evolution

Discovery of a peculiar Cepheid-like star towards the northern edge of the Small Magellanic Cloud ,

Context: R Coronae Borealis stars (RCB) are a rare type of evolved carbon-rich supergiant stars that are increasingly thought to result from the merger of two white dwarfs, called the Double degenerate scenario. This scenario is also studied as a source, at higher mass, of type Ia Supernovae (SnIa) explosions. Therefore a better understanding of RCBs composition would help to constrain simulations of such events. Aims: We searched for and studied RCB stars in the EROS Magellanic Clouds database. We also extended our research to DY Per type stars (DYPers) that are expected to be cooler RCBs (T ˜ 3500 K) and much more numerous than their hotter counterparts. With the aim of studying possible evolutionary connections between RCBs and DYPers, and also ordinary carbon stars, we compared their publically available broad band photometry in the optical, near, and mid-infrared. Methods: The light curves of ~70 millions stars, monitored for 6.7 years (from July 1996 to February 2003), have been analysed to search for the main signature of RCBs and DYPers: a large (up to 9 mag) drop in luminosity. Carbon stars with fading episodes were also found by inspecting numerous light curves of objects that presented an infrared excess in the 2MASS and Spitzer- SAGE and S^3MC databases. Follow-up optical spectroscopy was used to confirm each photometric candidate found. Results: We have discovered and confirmed 6 new Magellanic Cloud RCB stars and 7 new DYPers, but also listed new candidates: 3 RCBs and 14 DYPers. Optical and infrared colour magnitude diagrams that give new insights into these two sets of stars are discussed. We estimated a range of Magellanic RCB shell temperatures between 360 and 600 K. Conclusions: We confirm the wide range of absolute luminosity known for RCB stars, MV ˜ -5.2 to -2.6. Our study further shows that mid-infrared surveys are ideal to search for RCB stars, since they have thinner and cooler circumstellar shells than classical post-AGB stars. In addition, by increasing the number of known DYPers by ~400%, we have been able to shed light on the similarities in the spectral energy distribution between DYPers and ordinary carbon stars. We also observed that DYPer circumstellar shells are fainter and hotter than those of RCBs. This suggests that DYPers may simply be ordinary carbon stars with ejection events, but more abundance analysis is necessary to give a status on a possible evolutionnary connexion between RCBs and DYPers. Based on observations made with the CNRS/INSU MARLY telescope at the European Southern Observatory, La Silla, Chile. Figures 7-13 are only available in electronic form at http://www.aanda.org

Limits on the Macho Content of the Galactic Halo from the EROS-2 Survey of the Magellanic clouds

Rare types of variable star may give unique insight into short-lived stages of stellar evolution. The systematic monitoring of millions of stars and advanced light curve analysis techniques of microlensing surveys make them ideal for discovering also such rare variable stars. One example is the R Coronae Borealis (RCB) stars, a rare type of evolved carbon-rich supergiant. We have conducted a systematic search of the EROS-2 database for the Galactic catalogue Bulge and spiral arms to find Galactic RCB stars. The light curves of

Observation of microlensing toward the galactic spiral arms. EROS II 3 year survey

\sim