| Issue |
A&A
Volume 475, Number 3, December I 2007
|
|
|---|---|---|
| Page(s) | 1041 - 1052 | |
| Section | Stellar atmospheres | |
| DOI | https://doi.org/10.1051/0004-6361:20077923 | |
| Published online | 02 October 2007 | |
A refined analysis of the remarkable Bp star HR 6000*,**
1
Istituto Nazionale di Astrofisica–Osservatorio Astronomico di Trieste, via Tiepolo 11, 34131 Trieste, Italy e-mail: castelli@oats.inaf.it
2
European Southern Observatory, Casilla 19001, Santiago 19, Chile e-mail: shubrig@eso.org
Received:
22
May
2007
Accepted:
5
September
2007
Aims.UVES spectra of the very young (
years) peculiar B-type star HR 6000 were analyzed
in the near-UV and visual spectral regions (3050–9460 Å) with the aim of extending
to other spectral ranges the study made previously in the UV using IUE spectra.
Methods.
Stellar parameters Teff = 12 850 K, 
= 4.10, and 
km s-1,
as determined from H
, H
, H
Balmer profiles and
from the 
, 
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 (
) and c color indices.
The spectral analysis revealed: the
presence of emission lines for 
, 
, and ;
isotopic anomalies for Hg, Ca;
the presence of interstellar lines of 
at
3302.3, 3302.9, 5890, 5896 Å, and of 
at 7665, 7699 Å; the presence of a huge quantity of unidentified lines,
which we presume to be mostly due to 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 
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 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.
Key words: stars: abundances / line: identification / atomic data / stars: atmospheres / stars: chemically peculiar / stars: individual: HR 6000 (Bp)
© ESO, 2007
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