Stellar laboratories

Abstract

Context. For the spectral analysis of high-resolution and high-signal-to-noise spectra of hot stars, state-of-the-art non-local thermodynamic equilibrium (NLTE) model atmospheres are mandatory. These are strongly dependent on the reliability of the atomic data that is used for their calculation.Aims. To search for zirconium and xenon lines in the ultraviolet (UV) spectra of G191−B2B and RE 0503−289, new Zr iv-vii, Xe ivv, and Xe vii oscillator strengths were calculated. This allows, for the first time, determination of the Zr abundance in white dwarf (WD) stars and improvement of the Xe abundance determinations.Methods. We calculated Zr iv-vii, Xe iv-v, and Xe vii oscillator strengths to consider radiative and collisional bound-bound transitions of Zr and Xe in our NLTE stellar-atmosphere models for the analysis of their lines exhibited in UV observations of the hot WDs G191−B2B and RE 0503−289.Results. We identified one new Zr iv, 14 new Zr v, and ten new Zr vi lines in the spectrum of RE 0503−289. Zr was detected for the first time in a WD. We measured a Zr abundance of −3.5 ± 0.2 (logarithmic mass fraction, approx. 11 500 times solar). We identified five new Xe vi lines and determined a Xe abundance of −3.9 ± 0.2 (approx. 7500 times solar). We determined a preliminary photospheric Al abundance of −4.3±0.2 (solar) in RE 0503−289. In the spectra of G191−B2B, no Zr line was identified. The strongest Zr iv line (1598.948 Å) in our model gave an upper limit of −5.6 ± 0.3 (approx. 100 times solar). No Xe line was identified in the UV spectrum of G191−B2B and we confirmed the previously determined upper limit of −6.8 ± 0.3 (ten times solar). Conclusions. Precise measurements and calculations of atomic data are a prerequisite for advanced NLTE stellar-atmosphere modeling. Observed Zr iv-vi and Xe vi-vii line profiles in the UV spectrum of RE 0503−289 were simultaneously well reproduced with our newly calculated oscillator strengths.

Metal abundances in hot white dwarfs with signatures of a superionized wind

“…This is the consequence of on-going mass loss preventing gravitational settling . The most detailed analyzed DO with similar temperature is RE 0503-289 (70 000 K, log g = 7.5; Rauch et al 2017). With the exception of carbon, which is oversolar in RE other light metals (N,O,Si,P,and S) are underabundant by about one dex, in qualitative agreement with our DOs studied here.…”

Spectral Analysis of Moderately Charged Rare-Gas Atoms

“…Saloman [60][61][62] and an extension and new level optimization of the Ne IV spectrum, that includes our line identification on this gas, was recently made by A. Kramida [63]. Also our previous results a new Kr IV-VII oscillator strengths and an improved spectral analysis of the hot, hydrogen-deficient DO-type white dwarf RE 0503−289, and a new Zr IV-VII, Xe IV-V, and Xe VII oscillator strengths and the Al, Zr, and Xe abundances in the hot white dwarfs G191−B2B and RE 0503−289 were very recently reported [64,65].…”

Heavy metals in intermediate He-rich hot subdwarfs: the chemical composition of HZ 44 and HD 127493

“…HZ 44 is one of the very few hot subdwarf stars showing zirconium in its optical spectrum. We used the atomic data from Rauch et al (2017a) for our analysis. We fitted four distinct Zr iv lines in the HIRES spectrum of HZ 44 (Zr iv λλ 3576.…”