Hydrogen (H)

Bashkin, S.; Stoner, John O.

doi:10.1016/b978-0-7204-0322-0.50009-9

Cited by 102 publications

(85 citation statements)

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“…Table 2 summarizes the number of considered non-LTE levels and radiative transitions between them. All model atoms were built from the publicly available Tübingen Model Atom Database (TMAD 9 ), comprising data from different sources, namely Bashkin & Stoner (1975), the databases of the National Institute of Standards and Technology (NIST 10 ), the Opacity Project (OP 11 , Seaton et al 1994), the IRON project (Hummer et al 1993), CHIANTI 12 (Dere et al 1997;Landi et al 2013), as well as the Kentucky Atomic Line List 13 . For iron, we used a statistical approach employing typically seven superlevels per ion linked by superlines, together with an opacity sampling method (Anderson 1989;Rauch & Deetjen 2003).…”

Section: Model Atoms and Model Atmospheresmentioning

confidence: 99%

Analysis of HST/COS spectra of the bare C–O stellar core H1504+65 and a high-velocity twin in the Galactic halo

Werner

Rauch

2015

A&A

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H1504+65 is an extremely hot white dwarf (effective temperature T eff = 200 000 K) with a carbon-oxygen dominated atmosphere devoid of hydrogen and helium. This atmospheric composition was hitherto unique among hot white dwarfs (WDs), and it could be related to recently detected cooler WDs with C or O dominated spectra. The origin of the H and He deficiency in H1504+65 is unclear. To further assess this problem, we performed ultraviolet spectroscopy with the Cosmic Origins Spectrograph (COS) aboard the Hubble Space Telescope (HST). In accordance with previous far-ultraviolet spectroscopy performed with the Far Ultraviolet Spectroscopic Explorer, the most prominent lines stem from C iv, O v-vi, and Ne vi-viii. Archival HST/COS spectra are utilized to prove that the supersoft X-ray source RX J0439.8−6809 is, considering the exotic composition, a twin of H1504+65 that is even hotter (T eff = 250 000 K). In contrast to earlier claims, we find that the star is not located in the Large Magellanic Cloud but a foreground object in the Galactic halo at a distance of 9.2 kpc, 5.6 kpc below the Galactic plane, receding with v rad = +220 km s −1 .

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Section: Model Atoms and Model Atmospheresmentioning

confidence: 99%

Analysis of HST/COS spectra of the bare C–O stellar core H1504+65 and a high-velocity twin in the Galactic halo

Werner

Rauch

2015

A&A

View full text Add to dashboard Cite

show abstract

“…Table 6 summarizes the number of considered non-LTE levels and radiative transitions between them. All model atoms were built from the publicly available Tübingen Model Atom Database (TMAD 1 ), comprising data from different sources, namely Bashkin & Stoner (1975), the databases of the National Institute of Standards and Technology (NIST 2 ), the Opacity Project 3 (OP, Seaton et al 1994), CHIANTI 4 (Dere et al 1997;Landi et al 2013), as well as the Kentucky Atomic Line List 5 . For calcium and the iron-group elements (Sc-Ni), we used a statistical approach employing typically seven superlevels per ion linked by superlines, together with an opacity sampling method (Anderson 1989;Rauch & Deetjen 2003).…”

Section: Model Atoms and Model Atmospheresmentioning

confidence: 99%

The far-ultraviolet spectra of “cool” PG 1159 stars

Werner¹,

Rauch²,

Kruk³

2015

A&A

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We present a comprehensive study of Far Ultraviolet Spectroscopic Explorer (FUSE) spectra (912-1190 Å) of two members of the PG 1159 spectral class, which consists of hydrogen-deficient (pre-) white dwarfs with effective temperatures in the range T eff = 75 000-200 000 K. As two representatives of the cooler objects, we have selected PG 1707+427 (T eff = 85 000 K) and PG 1424+535 (T eff = 110 000 K), complementing a previous study of the hotter prototype PG 1159−035 (T eff = 140 000 K). The helium-dominated atmospheres are strongly enriched in carbon and oxygen, therefore, their spectra are dominated by lines from C iii-iv and O iii-vi, many of which were never observed before in hot stars. In addition, lines of many other metals (N, F, Ne, Si, P, S, Ar, Fe) are detectable, demonstrating that observations in this spectral region are most rewarding when compared to the near-ultraviolet and optical wavelength bands. We perform abundance analyses of these species and derive upper limits for several undetected light and heavy metals including iron-group and trans-iron elements. The results are compared to predictions of stellar evolution models for neutron-capture nucleosynthesis and good agreement is found.

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“…Table 3 summarizes the number of considered non-LTE levels and radiative transitions between them. All model atoms were built from the publicly available Tübingen Model Atom Database (TMAD 2 ), comprising data from different sources, namely Bashkin & Stoner (1975), the databases of the National Institute of Standards and Technology (NIST 3 ), the Opacity Project (OP 4 , Seaton et al 1994), CHIANTI 5 (Dere et al 1997;Landi et al 2013), as well as the Kentucky Atomic Line List 6 . Interstellar lines were modeled with the program Owens (Hébrard et al 2002;Hébrard & Moos 2003).…”

Section: Model Atoms and Model Atmospheresmentioning

confidence: 99%

HubbleSpace Telescope ultraviolet spectroscopy of the hottest known helium-rich pre-white dwarf KPD 0005+5106

Werner¹,

Rauch²

2015

A&A

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We present a model-atmosphere analysis of the ultraviolet echelle spectra of KPD 0005+5106 taken with the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope. The star is the hottest known pre-white dwarf (T eff = 200 000 ± 20 000 K, log g = 6.7 ± 0.3 (cm/s 2 )). Its atmosphere is composed of helium with trace amounts of metals. It is of the so-called O(He) spectral type that comprises very hot helium-rich pre-white dwarfs whose origin is debated. From neon and silicon ionisation balances, we derive tighter constraints on the effective temperature (195 000 ± 15 000 K) and improve previous abundance determinations of these elements. We confirm the idea that KPD 0005+5106 is the descendant of an R Coronae Borealis (RCB) star, so is the outcome of a binary-whitedwarf merger. We discuss the relation of KPD 0005+5106 to other O(He) and RCB stars.

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Hydrogen (H)

Cited by 102 publications

References 0 publications

Analysis of HST/COS spectra of the bare C–O stellar core H1504+65 and a high-velocity twin in the Galactic halo

Analysis of HST/COS spectra of the bare C–O stellar core H1504+65 and a high-velocity twin in the Galactic halo

The far-ultraviolet spectra of “cool” PG 1159 stars

HubbleSpace Telescope ultraviolet spectroscopy of the hottest known helium-rich pre-white dwarf KPD 0005+5106

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