| To gain insight into the chemical and magnetic evolution of upper-main sequence stars, we have undertaken a study of magnetic Ap stars in nearby northern open clusters with well-determined ages. Using the MuSiCoS spectropolarimeter on the 2 m Bernard Lyot telescope at Pic du Midi observatory, high-resolution (R = 35,000), moderate to high S/N (50--700) circular polarisation spectra have been obtained for 11 Ap stars (HD 19805, HD 21699, HD 23387, HD 23408, HD 23850, HD 28319, HD 171586, HD 171782, HD 205116, HD 205117, HD 205073) proposed as members of 5 open clusters (M39, IC 4756, the Pleiades, alpha Per and the Hyades). We determined chemical abundances using spectral line synthesis, with each elemental abundance determined based on multiple spectral lines, with the typical abundance uncertainty being 0.2 dex. Longitudinal magnetic field strengtl-1s were determined using Least Squares Deconvolved Stokes V profiles; with a typical uncertainty of about 100 gauss. Finally, projected rotational velocities were determined for each star, with a typical precision of 2 km/s. During the course of this study it became apparent that many of the stars studied are not in fact magnetic chemically peculiar stars. Some stars appear to be chemically normal, others appear to be other classes of non-magnetic chemically peculiar stars. Ultimately, it was concluded that only two of the observed stars are in fact magnetic chemically peculiar stars. Is this interesting and surprising finding purely a result of misclassification in the archival data, or does this say something important about the occurrences of magnetic chemically peculiar stars in open clusters? We present the results of this study, discussing the implications and providing suggestions for future research. |
