Stellar laboratories

Rauch, T.; Quinet, Pascal; Knörzer, M.; Hoyer, D.; Werner, K.; Kruk, J. W.; Demleitner, Markus

doi:10.1051/0004-6361/201730383

Cited by 22 publications

(22 citation statements)

References 43 publications

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“…These stars are unique probes for AGB nucleosynthesis since they show the intershell material at the surface and exhibit a strong enough wind to prevent processes like gravitational settling and radiative levitaion to tamper the original composition. The aim of this analysis is to consider atomic data of trans-iron elements (Z ≥ 30) that became available recently ( [9], and references therein) for a NLTE stellar-atmosphere calculation to determine abundances for a large set of elements to draw conclusions on the evolutionary history of these stars and on AGB nucleosynthesis.…”

Section: +23mentioning

confidence: 99%

Sliding along the Eddington Limit—Heavy-Weight Central Stars of Planetary Nebulae

Löbling

2018

Galaxies

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Due to thermal pulses, asymptotic giant branch (AGB) stars experience periods of convective mixing that provide ideal conditions for slow neutron-capture nucleosynthesis. These processes are affected by large uncertainties and are still not fully understood. By the lucky coincidence that about a quarter of all post-AGB stars turn hydrogen-deficient in a final flash of the helium-burning shell, they display nuclear processed material at the surface providing an unique insight to nucleosynthesis and mixing. We present results of non-local thermodynamic equilibrium spectral analyses of the extremely hot, hydrogen-deficient, PG 1159-type central stars of the Skull Nebula NGC 246 and the "Galactic Soccerballs" Abell 43 and NGC 7094.

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Section: +23mentioning

confidence: 99%

Sliding along the Eddington Limit—Heavy-Weight Central Stars of Planetary Nebulae

Löbling

2018

Galaxies

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“…The third DO discussed here (RE 0503−289, T eff = 70 000 K, log g = 7.5; Dreizler & Werner 1996) is a truly outstanding object with respect to its heavyelement variety. Fourteen trans-iron elements (see below) were identified and abundances determined (Rauch et al 2017, and references therein). Generally, large or extreme overabundances up to five dex oversolar were found, most probably caused by radiative levitation (Rauch et al 2016).…”

Section: Line Identification and Atomic Datamentioning

confidence: 99%

“…For our assessment of RE 0503−289 and PG 0109+111, we used spectra taken with the Far Ultraviolet Spectroscopic Explorer (FUSE) and the Hubble Space Telescope (HST). For details of the observations, we refer the reader to our earlier work (Rauch et al 2017;Hoyer et al 2018). In addition, we used coadded archival FUSE spectra of HD 149499 B.…”

Section: Line Identification and Atomic Datamentioning

confidence: 99%

First detection of bromine and antimony in hot stars

Werner¹,

Rauch²,

Knoerzer³

et al. 2018

A&A

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Bromine (atomic number Z = 35) and antimony (Z = 51) are extremely difficult to detect in stars. In very few instances, weak and mostly uncertain identifications of Br i, Br ii, and Sb ii in relatively cool, chemically peculiar stars were successful. Adopted solar abundance values rely on meteoritic determinations. Here, we announce the first identification of these species in far-ultraviolet spectra of hot stars (with effective temperatures of 49 500-70 000 K), namely in helium-rich (spectral type DO) white dwarfs. We identify the Br vi resonance line at 945.96 Å. A previous claim of Br detection based on this line is incorrect because its wavelength position is inaccurate by about 7 Å in atomic databases. Taking advantage of precise laboratory measurements, we identify this line as well as two other, subordinate Br vi lines. Antimony is detected by the Sb v resonance doublet at 1104.23/1225.98 Å as well as two subordinate Sb vi lines. A model-atmosphere analysis reveals strongly oversolar Br and Sb abundances that are caused by radiative-levitation dominated atomic diffusion.

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“…have computed oscillator strengths for tellurium ii-iii, including UV and optical lines. However, since the Te iii population numbers are low in HZ 44, none of these lines are visible Rauch et al (2017b). provided oscillator strengths for Te vi lines, including the resonance lines Te vi λλ 951.021, 1071.414 Å, which are visible in HZ 44 (see Fig…”

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confidence: 97%

“…In blue: a model with log Pb/H = −5.9 and log Sn/H = −6.9. In red: the same model without Pb and Sn.have been studied in white dwarfs byRauch et al (2016bRauch et al ( , 2017b. Despite the large number of Kr iv-v lines in the TOSS line list, none of them are strong enough in the final synthetic spectrum of HZ 44 to be identified in the observation.…”

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confidence: 99%

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

Dorsch¹,

Latour

Heber³

2019

A&A

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Context. Hot subluminous stars can be spectroscopically classified as subdwarf B (sdB) and O (sdO) stars. While the latter are predominantly hydrogen deficient, the former are mostly helium deficient. The atmospheres of most sdOs are almost devoid of hydrogen, whereas a small group of hot subdwarf stars of mixed H/He composition exists, showing extreme metal abundance anomalies. Whether such intermediate helium-rich (iHe) subdwarf stars provide an evolutionary link between the dominant classes is an open question.Aims. The presence of strong Ge, Sn, and Pb lines in the UV spectrum of HZ 44 suggests a strong enrichment of heavy elements in this iHe-sdO star and calls for a detailed quantitative spectral analysis focusing on trans-iron elements. Methods. Non-LTE model atmospheres and synthetic spectra calculated with TLUSTY/SYNSPEC are combined with high-quality optical, UV and FUV spectra of HZ 44 and its hotter sibling HD 127493 to determine their atmospheric parameters and metal abundance patterns.Results. By collecting atomic data from literature we succeeded to determine abundances of 29 metals in HZ 44, including the transiron elements Ga, Ge, As, Se, Zr, Sn, and Pb and provide upper limits for 10 other metals. This makes it the best described hot subdwarf in terms of chemical composition. For HD 127493 the abundance of 15 metals, including Ga, Ge, and Pb and upper limits for another 16 metals were derived. Heavy elements turn out to be overabundant by one to four orders of magnitude with respect to the Sun. Zr and Pb are among the most enriched elements.Conclusions. The C, N, and O abundance for both stars can be explained by nucleosynthesis of hydrogen burning in the CNO cycle along with their helium enrichment. On the other hand, the heavy-element anomalies are unlikely to be caused by nucleosynthesis. Instead diffusion processes are evoked with radiative levitation overcoming gravitational settlement of the heavy elements.

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Stellar laboratories

Cited by 22 publications

References 43 publications

Sliding along the Eddington Limit—Heavy-Weight Central Stars of Planetary Nebulae

Sliding along the Eddington Limit—Heavy-Weight Central Stars of Planetary Nebulae

First detection of bromine and antimony in hot stars

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

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