Stellar laboratories

Abstract

Context. For the spectral analysis of high-resolution and high signal-to-noise (S/N) 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. New Kr iv-vii oscillator strengths for a large number of lines enable us to construct more detailed model atoms for our NLTE model-atmosphere calculations. This enables us to search for additional Kr lines in observed spectra and to improve Kr abundance determinations.Methods. We calculated Kr iv-vii oscillator strengths to consider radiative and collisional bound-bound transitions in detail in our NLTE stellar-atmosphere models for the analysis of Kr lines that are exhibited in high-resolution and high S/N ultraviolet (UV) observations of the hot white dwarf RE 0503−289. Results. We reanalyzed the effective temperature and surface gravity and determined T eff = 70 000 ± 2000 K and log (g/cm s −2 ) = 7.5 ± 0.1. We newly identified ten Kr v lines and one Kr vi line in the spectrum of RE 0503−289. We measured a Kr abundance of −3.3 ± 0.3 (logarithmic mass fraction). We discovered that the interstellar absorption toward RE 0503−289 has a multi-velocity structure within a radial-velocity interval of −40 km s −1 < v rad < +18 km s −1 . Conclusions. Reliable measurements and calculations of atomic data are a prerequisite for state-of-the-art NLTE stellar-atmosphere modeling. Observed Kr v-vii line profiles in the UV spectrum of the white dwarf RE 0503−289 were simultaneously well reproduced with our newly calculated oscillator strengths.

Stellar laboratories

“…These were described in detail by Werner et al (2012b) and Rauch et al (2016b), respectively. For G191−B2B, we used the FUSE observation described by Rauch et al (2013) and the high-dispersion échelle spectrum (HST/STIS, 1145−3145 Å, R ≈ 100 000, Rauch et al 2013) available from the CALSPEC 1 database.…”

“…8) based on atomic data available at that time. Calculations of transition probabilities for Zn, Ga, Ge, Kr, Mo, Xe, and Ba in the subsequent years allowed precise abundance measurements for these elements (Rauch et al 2014a(Rauch et al , 2015b(Rauch et al , 2012(Rauch et al , 2016a(Rauch et al , 2014b(Rauch et al , 2015a(Rauch et al , 2016b.…”

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].…”

Overview of recent advances performed in the study of atomic structures and radiative processes for the lowest ionization stages of heavy elements

“…To fill this lack of atomic data, we recently started to compute transition rates for spectral lines belonging to three-through six-times ionized elements of interest using the HFR + CPOL + CPEN method. These studies allowed us to provide a large number of new reliable gf-values in Zr IV-VII [181], Mo IV-VII [182], Xe IV-VII [181,183], and Ba IV-VII [184] fifth-and sixth-row ions, in addition to Zn IV-VII [185], Ga IV-VII [186], Ge IV-VII [187], and Kr IV-VII [188] lighter ions. All these analyses, performed in collaboration with the Institute for Astronomy and Astrophysics of Eberhard Karls University in Tübingen, Germany, showed that, without exception, the abundances of those heavy metals in RE 0503-289 are unexpectedly strong supersolar (up to about 5 dex).…”

“…Mainly based on experimental energy levels, these were calculated with the semi-empirical HFR + CPOL + CPEN approach in accordance with the procedures described in detail in our different papers related to the search (and identification) of trans-iron elements in the hot white dwarfs G191-B2B and RE0503-289 [181][182][183][184][185][186][187][188]. More precisely, new radiative parameters for tens of thousands spectral lines in moderately charged fifth-and sixth-row ions, such as Zr IV-VII, Mo IV-VII, Tc IV-VII, Xe IV-VII, and Ba IV-VII, in addition to new atomic data obtained for the lighter ions Zn IV-VII, Ga IV-VII, Ge IV-VII, and Kr IV-VII are currently available in the database.…”