2000A&A...356..200G

This fifth paper in a sequence on abundance analyses of roAp stars features several improvements and complements over the previous investigations: i. The new vald-2 atomic data base was used which significantly improves the analysis of C, N, O, and rare earth elements (REE) and in particular includes also some doubly ionized REE species. ii. An individual opacity distribution function table was generated for a successful synthesis of photometric indices of this very peculiar star. iii. The influence of a (rather strong) magnetic field on abundance determinations is studied and presented for 30 elements. iv. Our investigation of 33 elements (45 ions) is the hitherto most complete chemical analysis of a chemically peculiar star, using modern tools. Similar to the four roAp stars analysed by us so far (α Cir: Kupka et al. 1996A&A...308..886K, HD 203932: Gelbmann et al. 1997A&A...319..630G, γ Equ: Ryabchikova et al. 1997A&A...322..234R, and HD 24712: Ryabchikova et al. 1997A&A...327.1137R) we find nearly solar abundances of Fe and Ni, and a definite overabundance of Cr and especially Co. Rare earth elements have large overabundances, whereas C and O are underabundant relative to the Sun. This pattern seems to be a common property of the chemically peculiar (CP2, Ap) stars. A new and most striking result is the discovery of the anomalous line strengths of the second ions of REE resulting in an abundance increase of up to +1.5dex, compared to values obtained from lines of the first ions. This anomaly is not found in non-roAp and ``normal'' stars.