[en] Accurate relative abundances have been obtained for carbon, oxygen, sodium, aluminium, silicon, and calcium in a sample of mildly metal-poor stars. This analysis complements a previous study carried out by Jehin et al. ([CITE], A&A, 341, 241), which provided the basis for the EASE scenario. This scenario postulates that field metal-poor stars were born in self-enriched proto-globular cluster clouds. By further investigating the correlations between the different alpha-element abundances, we propose a modified scenario for the formation of intermediate metallicity stars, in which the stars exhibiting lower than average alpha/Fe abundance ratios would form in low mass clouds, unable to sustain the formation of very massive stars (M ⪠30~M_o). Moreover, the carbon-to-iron ratio is found to decrease as one climbs the so-called Population IIb branch, i.e. when the s-element abundance increases. In the framework of the EASE scenario, we interpret this anticorrelation between the carbon and the s-element abundances as a signature of a hot bottom burning process in the metal-poor AGB stars which expelled the matter subsequently accreted by our Population IIb stars. Based on observations collected at the European Southern Observatory, La Silla, Chile (ESO Programmes 56.E-0384, 57.E-0400 and 59.E-0257).
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Decauwer, Hélène; Institute of Astrophysics and Geophysics, University of Liège, 17 Allée du 6 Août, 4000 Liège, Belgium
Jehin, Emmanuel ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique et traitement de l'image
Parmentier, Geneviève ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique et traitement de l'image
Magain, Pierre ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique et traitement de l'image
Language :
English
Title :
Abundance correlations in mildly metal-poor stars. II. Light elements (C to Ca)
Brown, J. H., Burkert, A., & Truran, J. W. 1995, ApJ, 440, 666
Cavallo, R. M., Pilachowski, C. A., & Rebolo, R. 1997, PASP, 109, 226
Delbouille, L., Roland, G., & Neven, L. 1973, Photometric Atlas of the Solar Spectrum from 3000 Å to 10000 Å, Institut d'Astrophysique, Université de Liège, Belgium
Gnedin, O. Y., & Ostriker, J. P., ApJ, 474, 223
Goriely, S., & Siess, L. 2001, A&A, 378, L25
Gratton, R. G., Carretta, E., Claudi, R., Lucatello, S., & Barbieri, M. 2003, A&A, 404, 187
Iwamoto, K., Brachwitz, F., Nomoto, K., et al. 1999, ApJS, 125, 439
Jehih, E., Magain, P., Neuforge, C., et al. 1999, A&A, 341, 241
Larson, R. B. 1998, MNRAS, 301, 569
Lattanzio, J., Forestini, M., & Charbonnel, C. 2000, Mem. Soc. Astron. It., 71, 737
Nakamura, F., & Umemura, M. 1999, ApJ, 515, 239
Nissen, P. E., & Schuster, W. J. 1997, A&A, 326, 751
Nissen, P. E. 1999, Ap&SS, 265, 249
Nissen, P. E., Primas, F., Asplund, M., & Lambert, D. L. 2002, A&A, 390, 235
Parmentier, G., Jehin, E., Magain, P., et al. 1999, A&A, 352, 138
Parmentier, G., Jehin, E., Magain, P., Noels, A., & Thoul, A. A. 2000, A&A, 363, 526
Parmentier, G., & Gilmore, G. 2001, A&A, 378, 97
Parmentier, G. 2004, MNRAS, 351, 585
Siess, L., Livio, M., & Lattanzio, J. 2002, ApJ, 570, 329
Thévenin, F., Charbonnel, C., de Freitas Pacheco, J. A., et al. 2001, A&A, 373, 905