A non-LTE spectral analysis of the3He and4He isotopes in the HgMn starκCancri

Maza, N. L.; Nieva, M. F.; Przybilla, N.

doi:10.1051/0004-6361/201425037

“…In particular, this applies to λ4472 Å, λ4922 Å, λ5016 Å, λ5875 Å, λ6678 Å as well as to λ7065 Å and again indicates that the helium abundance has to be lower in outer layers of the atmospheres than in deeper ones. This has also been reported for other 3 He (enriched) B-type stars like the main-sequence prototype HgMn star κ Cancri (Maza et al 2014) and for the well-studied BHB star Feige 86 (Bonifacio et al 1995). In fact, Bonifacio et al (1995) were also not able to simultaneously fit both the wings and the core of the analyzed absorption lines in the spectrum of Feige 86, although having calculated He profiles for a large variety of helium abundances, too.…”

Section: Helium Line Profile Anomaliessupporting

confidence: 74%

“…For a sophisticated quantitative spectral analysis we calculated synthetic model spectra using a detailed 3 He model atom which has been applied recently by Maza et al (2014) and a hybrid local thermodynamic/non-local thermodynamic equilibrium (LTE/NLTE) approach for B-type stars (Przybilla et al 2006a(Przybilla et al ,b, 2011Nieva & Przybilla 2007, 2008. This approach is based on the three generic codes ATLAS12 (Kurucz et al 1996), DETAIL and SURFACE (Giddings 1981; Butler & Giddings 1985, extended and updated).…”

Section: Model Atmospheres and Synthetic Spectramentioning

confidence: 99%

On the 3He anomaly in hot subdwarf B stars

Schneider¹,

Irrgang²,

Heber³

et al. 2017

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Decades ago, 3 He isotope enrichment in helium-weak B-type main-sequence, in blue horizontal branch and in hot subdwarf B (sdB) stars, i.e., helium-core burning stars of the extreme horizontal branch, were discovered. Diffusion processes in the atmosphere of these stars lead to the observed abundance anomalies. Quantitative spectral analyses of high-resolution spectra to derive photospheric isotopic helium abundance ratios for known 3 He sdBs have notbeen performed yet. We present preliminary results of high-resolution and high S/N spectra to determine the 3 He and 4 He abundances of nine known 3 He sdBs. We used a hybrid local/non-local thermodynamic equilibrium (LTE/NLTE) approach for B-type stars investigating multiple He lines, including λ4922 Å and λ6678 Å, which show the strongest isotopic shifts in the optical spectral range. We also report the discovery of four new 3 He sdBs from the ESO SupernovaProgenitor survey. Most of the 3 He sdBs cluster in a narrow temperature strip between ∼ 26000 K and ∼ 30000 K and have almost no atmospheric 4 He at all. Interestingly, three 3 He sdBs show evidence for vertical helium stratification.

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“…We also checkedNieva & Przybilla (2007) where these transitions are studied in LTE and NLTE. The recent analysis of helium lines in the HgMn star κ Cancri byMaza et al (2014) reveals a significant strengthening of a few He I lines prone to isotopic shifts, eg. λ 4921 Å and λ 6678 Å which we have not used to derive the helium abundance in the new HgMn star we found in this study.…”

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confidence: 99%

Chemical Composition of Intermediate-Mass Star Members of the M6 (Ngc 6405) Open Cluster

Kílíçoǧlu¹,

Monier²,

Richer³

et al. 2016

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We present here the first abundance analysis of 44 late B, A and F-type members of the young open cluster M6 (NGC 6405, age about 75 Myrs). Low and medium resolution spectra, covering the 4500 to 5800Å wavelength range, were obtained using the FLAMES/GIRAFFE spectrograph attached to the ESO Very Large Telescopes (VLT). We determined the atmospheric parameters using calibrations of the Geneva photometry and by adjusting the H β profiles to synthetic ones. The abundances of up to 20 chemical elements, from helium to mercury, were derived for 19 late B, 16 A and 9 F stars by iteratively adjusting synthetic spectra to the observations. We also derived a mean cluster metallicity of [Fe/H] = 0.07 ± 0.03 dex from the iron abundances of the F-type stars . We find that, for most chemical elements, the normal late B and A-type stars exhibit larger star-to-star abundance variations than the F-type stars do probably because of the faster rotation of the B and A stars. The abundances of C, O, Mg, Si and Sc appear to be anticorrelated to that of Fe, while the opposite holds for the abundances of Ca, Ti, Cr, Mn, Ni, Y, and Ba about as expected if radiative diffusion is efficient in the envelopes of these stars. In the course of this analysis, we discovered five new peculiar stars: one mild-Am, one Am, and one Fm star (HD 318091, CD-32 13109, GSC 07380-01211), one HgMn star (HD 318126), and one He-weak P-rich (HD 318101) star. We also discovered a new spectroscopic binary, most likely a SB2. We performed a detailed modelling of HD 318101,the new He-weak P-rich CP star, using the Montréal stellar evolution code XEVOL which treats self-consistently all particle transport processes. Although the overall abundance pattern of this star is properly reproduced, we find that detailed abundances (in particular the high P excess) resisted modelling attempts even when a range of turbulence profiles and mass loss rates were considered. Solutions -4are proposed, which are still under investigation. Subject headings: stars: abundances -open clusters: individual(M6) -stars individual: HD 318101stars in open clusters, with a variety of goals (Stütz et al. 2006;Villanova et al. 2009;Pace et al. 2010;Pancino et al. 2010; Jacobson et al. 2011;Carrera & Pancino 2011;Carraro et al. 2014).In this paper, we present the first abundance analysis of 44 late B, A and F-type dwarfs members of the young open cluster M6. M6 (NGC 6405) is an interarm object lying between the local arm and the Sagittarius arm (Vleeming 1974). It is a moderately-rich cluster (van den Bergh & Hagen 1975) and it contains about 120 most-likely members (for V ≤ 15.1) according to Antalová (1972). Previous age, distance, color excess and metallicity determinations for the cluster are collected in Table 1, along with our determinations (see Sec. 4.1.2 and 2.1). Early estimates of the distance, reddening and age of the cluster were obtained photometrically by Rohlfs et al. (1959) 1 who derived a distance of 630 pc from photoelectric UBV observations of 132 stars, a mean reddening E(B...

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“…For a sophisticated quantitative spectral analysis we calculated synthetic model spectra using a detailed 3 He model atom which has been applied recently by Maza et al (2014) and a hybrid local thermodynamic/non-local thermodynamic equilibrium (LTE/NLTE) approach for B-type stars (Przybilla et al 2006a(Przybilla et al ,b, 2011Nieva & Przybilla 2007, 2008. This approach is based on the three generic codes ATLAS12 (Kurucz et al 1996), DETAIL and SURFACE (Giddings 1981; Butler & Giddings 1985, extended and updated).…”

Section: Model Atmospheres and Synthetic Spectramentioning

confidence: 99%

On the ³He anomaly in hot subdwarf B stars

Schneider

¹

,

Irrgang

²

,

Heber

³

et al. 2017

Open Astronomy

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1

0

View full text Add to dashboard Cite

Decades ago, 3 He isotope enrichment in helium-weak B-type main-sequence, in blue horizontal branch and in hot subdwarf B (sdB) stars, i.e., helium-core burning stars of the extreme horizontal branch, were discovered. Diffusion processes in the atmosphere of these stars lead to the observed abundance anomalies. Quantitative spectral analyses of high-resolution spectra to derive photospheric isotopic helium abundance ratios for known 3 He sdBs have notbeen performed yet. We present preliminary results of high-resolution and high S/N spectra to determine the 3 He and 4 He abundances of nine known 3 He sdBs. We used a hybrid local/non-local thermodynamic equilibrium (LTE/NLTE) approach for B-type stars investigating multiple He lines, including λ4922 Å and λ6678 Å, which show the strongest isotopic shifts in the optical spectral range. We also report the discovery of four new 3 He sdBs from the ESO SupernovaProgenitor survey. Most of the 3 He sdBs cluster in a narrow temperature strip between ∼ 26000 K and ∼ 30000 K and have almost no atmospheric 4 He at all. Interestingly, three 3 He sdBs show evidence for vertical helium stratification.

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A non-LTE spectral analysis of the³He and⁴He isotopes in the HgMn starκCancri

Cited by 12 publications

References 30 publications

On the 3He anomaly in hot subdwarf B stars

On the 3He anomaly in hot subdwarf B stars

Chemical Composition of Intermediate-Mass Star Members of the M6 (Ngc 6405) Open Cluster

On the ³He anomaly in hot subdwarf B stars

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