2007A&A...475.1041C

UVES spectra of the very young (∼10⁷ years) peculiar B-type star HR6000 were analyzed in the near-UV and visual spectral regions (3050-9460Å) with the aim of extending to other spectral ranges the study made previously in the UV using IUE spectra. Stellar parameters T_eff=12850K, logg=4.10, and ξ=0km/s, as determined from H_β, H_γ, H_δ Balmer profiles and from the FeI, FeII ionization equilibrium, were used to compute an individual abundances ATLAS12 model. We identified spectral peculiarities and obtained final stellar abundances by comparing observed and computed equivalent widths and line profiles. The adopted model fails to reproduce the (b-y) and c color indices. The spectral analysis revealed: the presence of emission lines for MnII, CrII, and FeII; isotopic anomalies for Hg, Ca; the presence of interstellar lines of NaI at λλ 3302.3, 3302.9, 5890, 5896Å, and of KI at 7665, 7699Å; the presence of a huge quantity of unidentified lines, which we presume to be mostly due to FeII transitions owing to the large Fe overabundance amounting to [+0.7]. The main chemical peculiarities are an extreme overabundance of Xe, followed by those of Hg, P, Y, Mn, Fe, Be, and Ti. The most underabundant element is Si, followed by C, N, Al, S, Mg, V, Sr, Co, Cl, Sc, and Ni. The silicon underabundance [-2.9] is the lowest value for Si ever observed in any HgMn star. The observed lines of HeI cannot be reproduced by a single value of the He abundance, but they require values ranging from [-0.8] to [-1.6]. Furthermore, when the observed and computed wings of HeI lines are fitted, the observed line cores are much weaker than the computed ones. From the present analysis we infer the presence of vertical abundance stratification for He, Mn, and possibly also Fe and P.