Experimental isotopic shifts in Ni II and Fe II

Rosberg, Maria; Litzén, Ulf; Johansson, Sveneric

doi:10.1093/mnras/262.1.l1

Cited by 10 publications

(5 citation statements)

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“…A(Ni) 300 8.71 ± 0.06 6.13 ± 0.14 400 8.71 ± 0.06 6.14 ± 0.14 800 8.70 ± 0.05 6.15 ± 0.13 derive from observed spectra because the line is weaker, or perhaps because there are uncertainties in the wavelengths of the Ni isotopic components (see Rosberg et al 1993). The results of the Monte Carlo tests give an indication that the systematics dominate the error budget.…”

Section: S /N a (O)mentioning

confidence: 99%

The photospheric solar oxygen project

Caffau

Ludwig

Steffen

et al. 2015

A&A

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Context. The solar photospheric abundance of oxygen is still a matter of debate. For about ten years some determinations have favoured a low oxygen abundance which is at variance with the value inferred by helioseismology. Among the oxygen abundance indicators, the forbidden line at 630 nm has often been considered the most reliable even though it is blended with a Ni i line. In Papers I and II of this series we reported a discrepancy in the oxygen abundance derived from the 630 nm and the subordinate [O I] line at 636 nm in dwarf stars, including the Sun. Aims. Here we analyse several, in part new, solar observations of the centre-to-limb variation of the spectral region including the blend at 630 nm in order to separate the individual contributions of oxygen and nickel. Methods. We analyse intensity spectra observed at different limb angles in comparison with line formation computations performed on a CO5BOLD 3D hydrodynamical simulation of the solar atmosphere. Results. The oxygen abundances obtained from the forbidden line at different limb angles are inconsistent if the commonly adopted nickel abundance of 6.25 is assumed in our local thermodynamic equilibrium computations. With a slightly lower nickel abundance, A(Ni) ≈ 6.1, we obtain consistent fits indicating an oxygen abundance of A(O) = 8.73 ± 0.05. At this value the discrepancy with the subordinate oxygen line remains. Conclusions. The derived value of the oxygen abundance supports the notion of a rather low oxygen abundance in the solar photosphere. However, it is disconcerting that the forbidden oxygen lines at 630 and 636 nm give noticeably different results, and that the nickel abundance derived here from the 630 nm blend is lower than expected from other nickel lines.

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Section: S /N a (O)mentioning

confidence: 99%

The photospheric solar oxygen project

Caffau

Ludwig

Steffen

et al. 2015

A&A

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“…The two main components are 58 Ni i and 60 Ni i, with an isotopic ratio of 0.38 and λ of 630.0335 nm and 630.0355 nm, respectively (see Bensby et al 2004). Each component of the nickel blend is assumed to have log g f = −2.11 (Johansson et al 2003 Rosberg et al 1993). Rosberg et al (1993) studied the isotope splitting of the even components of Ni ii and showed that the splitting is equidistant for any of the even components of Ni ii they studied.…”

Section: [Oi] 630 Nmmentioning

confidence: 99%

“…Each component of the nickel blend is assumed to have log g f = −2.11 (Johansson et al 2003 Rosberg et al 1993). Rosberg et al (1993) studied the isotope splitting of the even components of Ni ii and showed that the splitting is equidistant for any of the even components of Ni ii they studied. We assume the same behaviour for Ni i.…”

Section: [Oi] 630 Nmmentioning

confidence: 99%

The photospheric solar oxygen project

Caffau¹,

Ludwig

Steffen

et al. 2008

A&A

264

305

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Context. The solar oxygen abundance has undergone a major downward revision in the past decade, the most noticeable one being the update including 3D hydrodynamical simulations to model the solar photosphere. Up to now, such an analysis has only been carried out by one group using one radiation-hydrodynamics code. Aims. We investigate the photospheric oxygen abundance considering lines from atomic transitions. We also consider the relationship between the solar model used and the resulting solar oxygen abundance, to understand whether the downward abundance revision is specifically related to 3D hydrodynamical effects. Methods. We performed a new determination of the solar photospheric oxygen abundance by analysing different high-resolution high signal-to-noise ratio atlases of the solar flux and disc-centre intensity, making use of the latest generation of CO5BOLD 3D solar model atmospheres. Results. We find 8.73 ≤ log (N O /N H ) + 12 ≤ 8.79. The lower and upper values represent extreme assumptions on the role of collisional excitation and ionisation by neutral hydrogen for the NLTE level populations of neutral oxygen. The error of our analysis is ± (0.04± 0.03) dex, the last being related to NLTE corrections, the first error to any other effect. The 3D "granulation effects" do not play a decisive role in lowering the oxygen abundance. Conclusions. Our recommended value is log (N O /N H ) = 8.76 ± 0.07, considering our present ignorance of the role of collisions with hydrogen atoms on the NLTE level populations of oxygen. The reasons for lower O abundances in the past are identified as (1) the lower equivalent widths adopted and (2) the choice of neglecting collisions with hydrogen atoms in the statistical equilibrium calculations for oxygen.

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“…Each component of the nickel blend is assumed to have log g f =−2.11 (Johansson et al 2003). The other two even isotopic components, 62 Ni i and 64 Ni i, can be inserted in the line list as well, even if this does not change significantly the line shape, assuming that their shift with respect to the other even components has the same value as the shift between 58 Ni i and 60 Ni i (about 0.002 nm, see Rosberg et al 1993). Rosberg et al (1993) studied the isotope splitting of the even components of Ni ii and showed that the splitting is equidistant for any of the even components of Ni ii they studied.…”

Section: [Oi] 630 Nmmentioning

confidence: 99%

The photospheric solar oxygen project: I. Abundance analysis of atomic lines and influence of atmospheric models

Caffau,

Ludwig,

Steffen

et al. 2008

Preprint

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Context. The solar oxygen abundance has undergone a major downward revision in the last decade, the most noticeable one being the update including 3D hydrodynamical simulations to model the solar photosphere. Up to now, such an analysis has been carried out only by one group using one radiation-hydrodynamics code. Aims. We investigate the photospheric oxygen abundance considering lines from atomic transitions. We also consider the relationship between the solar model used and the resulting solar oxygen abundance, to understand whether the downward abundance revision is specifically related to 3D hydrodynamical effects. Methods. We perform a new determination of the solar photospheric oxygen abundance by analysing different high-resolution high signal-to-noise ratio atlases of the solar flux and disc-centre intensity making use of the latest generation of CO5BOLD 3D solar model atmospheres. Results. We find 8.73 ≤ log(N O /N H ) + 12 ≤ 8.79. The lower and upper values represent extreme assumptions on the role of collisional excitation and ionisation by neutral hydrogen for the NLTE level populations of neutral oxygen. The error of our analysis is ± (0.04± 0.03) dex, the last being related to NLTE corrections, the first error to any other effect. 3D "granulation effects" do not play a decisive role in lowering the oxygen abundance. Conclusions. Our recommended value, considering our present ignorance of the role of collisions with hydrogen atoms on the NLTE level populations of oxygen, is log(N O /N H ) = 8.76 ± 0.07. The reasons which have led to lower O abundances in the past are identified as (1) the lower equivalent widths adopted, and (2) the choice of neglecting collisions with hydrogen atoms in the statistical equilibrium calculations for oxygen.

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Experimental isotopic shifts in Ni II and Fe II

Cited by 10 publications

References 0 publications

The photospheric solar oxygen project

The photospheric solar oxygen project

The photospheric solar oxygen project

The photospheric solar oxygen project: I. Abundance analysis of atomic lines and influence of atmospheric models

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