![]() ![]() They announced new experimental work to improve the Xe ii atomic data. In their discussion on the wavelength accuracy, Hansen & Persson ( 1987) pointed out that the wavelength accuracy for many lines is too low to be satisfactory, mostly owing to the widely varying quality of the experimental data they used. The most complete work on Xe ii is that of Hansen & Persson ( 1987), who analyzed all the published (Boyce 1936 Humphreys 1939) and unpublished Xe ii lines from 392 Å to 10 220 Å obtained in laboratory by Humphreys and Boyce. In addition, we noticed that the wavelengths of several Xe ii lines are close, but not coincident with the wavelength of some unidentified stellar lines (Castelli & Hubrig 2007), so that we wondered about the accuracy of the wavelength determination from laboratory spectra. As a consequence, the computed spectra do not include numerous Xe ii lines, raising the doubt that some unidentified lines could just be due to Xe ii. The xenon overabundance implies the presence of numerous Xe ii lines in the spectra of the HgMn stars, but the Xe ii transition probabilities are very incomplete, when we compare the large number of transitions listed in the NIST database and the small number of them with an associated log gf-value. ![]() This is, for instance, the case of κ Cnc and 33 Gem, for which abundances equal to −4.87 ± 0.13 dex and −4.90 ± 0.07 dex were determined by Dworetsky et al. Several studies of mercury-manganese (HgMn) stars have pointed out the presence of xenon with overabundances up to 5 dex relative to the solar value log ( N Xe/ N tot) = − 9.87 (Grevesse & Sauval 1998). Key words: atomic data / stars: individual: HR 6000 / stars: chemically peculiar / stars: individual: HD 71066 / stars: individual: 46 Aql / stars: individual: HD 175640 We adopted the average of the oscillator strengths derived from the four stars as final astrophysical oscillator strength. We find that the Xe ii stellar oscillator strengths may differ from one star to another from 0.0 dex to 0.3 dex. We find that all the lines with wavelengths related to the 6d and 7s energy levels have a corresponding unidentified spectral line, blueshifted by the same quantity of about 0.1 Å in all the four stars, so that we identified these lines as coming from Xe ii and modified their NIST wavelength value according to the observed stellar value. In this framework, we performed a complete abundance analysis of HD 71066, while we relied on our previous works for the other stars. We checked the stellar atomic data derived from HR 6000 by using them to compute synthetic spectra for three other xenon-overabundant, slowly rotating HgMn stars, HD 71066, 46 Aql, and HD 175640. We derived astrophysical oscillator strengths for all the Xe ii observed lines and compared them with the literature values, when available. We compared the Xe ii wavelengths listed in the NIST database with the position of the lines observed in the high-resolution UVES spectrum of the xenon-overabundant, slowly rotating HgMn star HR 6000, and we modified them when needed. For these reasons we investigated the Xe ii lines lying in the 3900–4521 Å, 4769–7542 Å, and 7660–8000 Å spectral ranges of four well-studied HgMn stars. In addition, some predicted Xe ii lines are redshifted by about 0.1 Å from stellar unidentified lines, raising the question about the wavelength accuracy of the Xe ii line data available in the literature. As a consequence, several unidentified lines in the spectra of HgMn stars could be due to Xe ii. In spite of large overabundances of Xe ii observed in numerous mercury-manganese (HgMn) stars, Xe ii oscillator strengths are only available for a very limited number of transitions. Istituto Nazionale di Astrofisica, Osservatorio Astronomico diĮ-mail: University, Faculty of Science, Department of Astronomy andĪstrophysical Institute Potsdam, An der Sternwarte 16, 14482Īims. Astronomical objects: linking to databases.Including author names using non-Roman alphabets.Suggested resources for more tips on language editing in the sciences Punctuation and style concerns regarding equations, figures, tables, and footnotes ![]()
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