Wavelengths and oscillator strengths of Xe II from the UVES spectra of four HgMn stars

Abstract

Aims. 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. As a consequence, several unidentified lines in the spectra of HgMn stars could be due to Xe ii. 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. 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. Methods. 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. We derived astrophysical oscillator strengths for all the Xe ii observed lines and compared them with the literature values, when available. 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. In this framework, we performed a complete abundance analysis of HD 71066, while we relied on our previous works for the other stars. Results. 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. 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 adopted the average of the oscillator strengths derived from the four stars as final astrophysical oscillator strength.

Atomic diffusion in the atmosphere of Feige 86

“…λ4180, λ4208, λ4245, λ4330, λ4462 Å) show a ∼ 0.1 Å blue shift, which indicates that we see different isotopes at once, similar to the case of helium. The radial velocity shift of the lines corresponds to the isotopic shifts observed in CP stars (Yüce et al, 2011). Past studies have reported Xe, Bi and other heavy elements in Feige 86 (Bonifacio et al 1995, Castelli et al 1997.…”

Spectroscopic abundance analyses of the 3He stars HD 185330 and 3 Cen A

“…When no data are found in the database, we use log gf values given in the VALD3 database (Ryabchikova et al 2015) (Mn II, Fe III, and Ni II). We can find no data of atomic transition probabilities for two ions Ga II and Xe II in these databases and use data taken from Hubrig et al (2014) and stellar log gf values given in Yüce et al (2011), respectively. Effects of isotopic or hyperfine structures for Mn II, Ga II, and Hg II have not been taken into acount in this study.…”

Elemental abundance analyses with DAO spectrograms: XL

“…We identified the stellar lines with the help of the general references A Multiplet Table of Astrophysical Interest (Moore, ) and Wavelengths and Transition Probabilities for Atoms and Atomic Ions, Part 1 (Reader & Corliss, ) as well as Pettersson () for S II, Huldt, Johansson, Litzen, and Wyart () for Ti II, Catalan, Meggers, and Garcia‐Riquelme () for Mn I, Iglesias and Velasco () for Mn II, Nave, Johansson, Learner, Thorne, and Brault () for Fe I, and Dworetsky (), Johansson (), Guthrie (), and Adelman () for Fe II, Nilsson, Johasson, and Kurucz () for Y II, and Yüce, Castelli, and Hubrig () for Xe II. The spectrum of HR 196 exhibits lines of CI, Mg II, AlI, Si II, Ca I, Ca II, Sc II, Ti II, V II, Cr I, Cr II, Mn I, Fe I, Fe II, NiI, Ni II, Sr II, and Ba II.…”

“…It includes for each line the multiplet number (Moore, ), the laboratory wavelength, the logarithm of the gf‐value and its source, the equivalent width (in mÅ) as observed, and the deduced abundance. For some species, letters replace multiplet numbers to indicate sources other than Moore (): I, Iglesias and Velasco (); J, Johansson (); K, Kurucz and Bell (); and Y, Yüce et al (). For comparison purpose, we used the solar values of Asplund et al (), Grevesse, Scott, Asplund, and Sauval (), and Scott et al (, ).…”

“…References: BG, Biemont et al (); DL = den Hartog, Lawler, Sneden, and Cowan (); FW = Fuhr and Wiese () for Ca I and Fuhr and Wiese () for Fe I and Fe II; HI = Hibbert (); HL = Hannaford, Lowe, Grevesse, and Biemont (); JS = Jugaku, Sargent, and Greenstein (); K1 = Kelleher and Podobedova (); K2 = Kelleher and Podobedova (); K3 = Kelleher and Podobedova (); KP = Kurucz and Peytremann (1975); KX = Kurucz and Bell (); LD = Lawler and Dankin (); MF = Fuhr, Martin, and Wiese (); Martin, Fuhr, and Wiese (); NL = Nilsson et al (2006); PK = Podebedova, Kelleher, and Wiese (); SL = Sobeck et al (2007); VA = Vald Database; WF = Wiese, Fuhr, and Deters (); WL = Wood et al (2013); WM = Wiese and Martin (); WS = Wiese, Smith, and Glennon (); Wiese, Smith, and Miles (); YC = Yüce et al ().…”