A refined analysis of the remarkable Bp star HR 6000

Abstract

Aims. UVES spectra of the very young ( ∼ 10 7 years) peculiar B-type star HR 6000 were analyzed in the near-UV and visual spectral regions (3050-9460 Å) with the aim to extend to other spectral ranges the study made previously in the UV using IUE spectra. Methods. Stellar parameters T eff =12850 K, log g=4.10, and ξ=0 km s −1 , as determined from H β , H γ , H δ Balmer profiles and from the Fe i, Fe ii 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.Results. The adopted model fails to reproduce the (b-y) and c color indices. The spectral analysis has revealed: the presence of emission lines for Mn ii, Cr ii, and Fe ii; isotopic anomalies for Hg , Ca ; the presence of interstellar lines of Na i at λλ 3302.3, 3302.9, 5890, 5896 Å, and of K i at 7665, 7699 Å; the presence of a huge quantity of unidentified lines, which we presume to be mostly due to Fe ii 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 He i can not 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 He i 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 P.

First spectroscopic analysis of β Scorpii C and β Scorpii E

“…The pattern that we show in Fig. 3 is very similar to that derived for HR 6000, another HgMn star, studied in detail by Catanzaro et al (2004) and Castelli & Hubrig (2007). The latter authors tried to explain its peculiarity by considering chemical stratification within the atmosphere.…”

A non-LTE spectral analysis of the3He and4He isotopes in the HgMn starκCancri

“…6). This is a clear sign that the element is not homogeneously distributed A112, page 3 of 7 A&A 572, A112 (2014) throughout the atmosphere, but instead shows a vertical abundance stratification, which is unusual in HgMn stars and has been reported for only a few objects so far (Dworetsky 2004;Castelli & Hubrig 2007 Table 2, together with the Rosseland optical depths τ ross at which the line cores are formed. The abundance ratio 3 He/ 4 He is about 0.25 to 0.30 at the atmospheric depths covered by the observations, slightly lower than the value of 0.35 derived by Zakharova & Ryabchikova (1996).…”

New Fe ii energy levels from stellar spectra

“…The observed levels come from the following sources: Johansson (1978), Sugar & Corliss (1985), Adam et al (1987), Johansson & Baschek (1988), Johansson (1988, private comm. ), Rosberg & Johansson (1992), Castelli et al (2008), Castelli et al (2009), and this work. The calculations on the web site are updated whenever there are improvements to the energy levels.…”

“…The new levels have allowed us to identify more than the 50% of the previously unidentified lines in the wavelength region 3800−8000 Å of HR 6000 (Castelli & Hubrig 2007). The method that we adopted to determine the new energy levels is the same as described in Paper I.…”

“…In a previous paper (Castelli et al 2009) (Paper I) we have determined 21 new 3d 6 ( 3 H)4f high energy levels of Fe ii on the basis of predicted energy levels, computed log g f values for Fe ii, and unidentified lines in UVES high resolution, high signal-to-noise spectra of HR 6000 and 46 Aql. Both stars are iron overabundant CP stars and have rotational velocity v sin i of the order of 1.5 km s −1 and 1.0 km s −1 , respectively.…”