Chemical evolution of A- and B-type stars in open clusters: observed abundances vs. diffusion models. Am stars in the Praesepe cluster

Rok, strany: 2008, 123 - 128

We have decided to address the problem of how abundances and peculiarities change during main sequence evolution. We have setup a program to measure the atmospheric abundance patterns from tens of A-type star members of clusters of different ages, and compare the results with theory predictions. In this paper we present the overall project and we focus on the results obtained for a sample of Am stars of the Praesepe cluster (log t = 8.85 ± 0.15; González-García et al., 2006). We have obtained spectra for eight Am stars, two normal A-type stars and one blue straggler, that are probable members of the Praesepe cluster. For all of these stars we have determined fundamental parameters and photospheric abundances for a large number of chemical elements. For seven stars we also obtained spectra in circular polarisation and applied the LSD technique to measure the mean longitudinal magnetic field. We have found good agreement between abundance predictions of diffusion models and measured abundances, except for Na and S. Li appears to be overabundant in three stars of our sample. No magnetic field was detected in any of the analysed stars.

ISO 690:

Fossati, L., Bagnulo, S., Monier, R., Khan, S., Kochukhov, O., Landstreet, J., Wade, G., Weiss, W. 2008. Chemical evolution of A- and B-type stars in open clusters: observed abundances vs. diffusion models. Am stars in the Praesepe cluster. In Contributions of the Astronomical Observatory Skalnaté Pleso, vol. 38, no.2, pp. 123-128. 1335-1842.

APA:

Fossati, L., Bagnulo, S., Monier, R., Khan, S., Kochukhov, O., Landstreet, J., Wade, G., Weiss, W. (2008). Chemical evolution of A- and B-type stars in open clusters: observed abundances vs. diffusion models. Am stars in the Praesepe cluster. Contributions of the Astronomical Observatory Skalnaté Pleso, 38(2), 123-128. 1335-1842.