The photospheric solar oxygen project

Caffau, E.; Ludwig, H.‐G.; Steffen, M.; Ayres, Thomas R.; Bonifacio, P.; Cayrel, Roger; Freytag, B.; Plez, B.

doi:10.1051/0004-6361:200809885

Cited by 267 publications

(335 citation statements)

References 52 publications

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“…According to our own previous studies (Caffau et al 2008, hereafter Paper I), the solar oxygen abundance is somewhat higher, A(O) = 8.73−8.79 dex, with a weighed mean of A(O) = 8.76 ± 0.07 dex. This rather high oxygen abundance was supported by the work of Ayres et al (2013), who used a CO5BOLD model atmosphere to analyze molecular CO lines (assuming n(C)/n(O) = 0.5) and derived A(O) = 8.78 ± 0.02 dex.…”

Section: Introductionmentioning

confidence: 78%

The photospheric solar oxygen project

Steffen

Prakapavičius

Caffau

et al. 2015

A&A

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109

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Context. The solar photospheric oxygen abundance is still widely debated. Adopting the solar chemical composition based on the "low" oxygen abundance, as determined with the use of three-dimensional (3D) hydrodynamical model atmospheres, results in a well-known mismatch between theoretical solar models and helioseismic measurements that is so far unresolved. Aims. We carry out an independent redetermination of the solar oxygen abundance by investigating the center-to-limb variation of the O i IR triplet lines at 777 nm in different sets of spectra.Methods. The high-resolution and high signal-to-noise solar center-to-limb spectra are analyzed with the help of detailed synthetic line profiles based on 3D hydrodynamical CO5BOLD model atmospheres and 3D non-LTE line formation calculations with NLTE3D. The idea is to exploit the information contained in the observations at different limb angles to simultaneously derive the oxygen abundance, A(O), and the scaling factor S H that describes the cross-sections for inelastic collisions with neutral hydrogen relative to the classical Drawin formula. Using the same codes and methods, we compare our 3D results with those obtained from the semiempirical Holweger-Müller model atmosphere as well as from different one-dimensional (1D) reference models. Results. With the CO5BOLD 3D solar model, the best fit of the center-to-limb variation of the triplet lines is obtained when the collisions by neutral hydrogen atoms are assumed to be efficient, i.e., when the scaling factor S H is between 1.2 and 1.8, depending on the choice of the observed spectrum and the triplet component used in the analysis. The line profile fits achieved with standard 1D model atmospheres (with fixed microturbulence, independent of disk position μ) are clearly of inferior quality compared to the 3D case, and give the best match to the observations when ignoring collisions with neutral hydrogen (S H = 0). The results derived with the Holweger-Müller model are intermediate between 3D and standard 1D. Conclusions. The analysis of various observations of the triplet lines with different methods yields oxygen abundance values (on a logarithmic scale where A(H) = 12) that fall in the range 8.74 < A(O) < 8.78, and our best estimate of the 3D non-LTE solar oxygen abundance is A(O) = 8.76 ± 0.02. All 1D non-LTE models give much lower oxygen abundances, by up to −0.15 dex. This is mainly a consequence of the assumption of a μ-independent microturbulence. An independent determination of the relevant collisional cross-sections is essential to substantially improve the accuracy of the oxygen abundance derived from the O i IR triplet.

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Section: Introductionmentioning

confidence: 78%

The photospheric solar oxygen project

Steffen

Prakapavičius

Caffau

et al. 2015

A&A

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109

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“…Intermediate (Caffau et al 2008) and high (this work) abundances may be obtained from 3D models as well. Furthermore, given the sensitivity of the results to the details of the analysis, we should also question to what degree an analysis based on equivalent widths (which is what has been employed in most cases thus far) is enough to capture all the subtleties that are observed in a detailed fit.…”

Section: Discussionmentioning

confidence: 96%

“…The debate on whether the proposed revision should be adopted has been very intense, and several papers have been published with new abundance determinations, including those of Ayres et al (2006), Socas-Navarro & Norton (2007), Ayres (2008), Centeno & Socas-Navarro (2008), Caffau et al (2008, 2011), Scott et al (2009), Pereira et al (2009. The frequency of publications on the so-called solar oxygen crisis seems to have declined in recent years, not because the problem has been satisfactorily resolved, but probably because there are no new arguments or data in favor of one view or the other.…”

Section: Introductionmentioning

confidence: 99%

“…Ayres (2008) correctly remarked that while a 3D atmosphere is preferable over a 1D atmosphere, it is not clear that A&A 577, A25 (2015) a model resulting from a numerical simulation is better than an empirical one when it is employed to fit observations. In addition, the work of Caffau et al (2008Caffau et al ( , 2011 demonstrated that working in 3D does not necessarily result in lower abundances. The present paper is an attempt to resolve the dilemma of theoretical 3D versus empirical 1D by taking the best of both approaches.…”

Section: Introductionmentioning

confidence: 99%

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The solar oxygen abundance from an empirical three-dimensional model

Socas‐Navarro

2015

A&A

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The oxygen abundance in the solar photosphere, and consequently the solar metallicity itself, is still a controversial question with farreaching implications in many areas of astrophysics. This paper presents a new determination obtained by fitting the forbidden O i line at 6300 Å with an observational 3D model. The approach presented here is novel because previous determinations were based either on 1D empirical stratifications or on 3D theoretical models. The resulting best-fit abundances are log (O) = 8.90 and log (Ni) = 6.15. Nevertheless, by introducing minor tweaks in the model and the procedure, it is possible to retrieve very different values, even down to log (O) = 8.70. This extreme sensitivity of the abundance to possible systematic effects is not specific to this particular work, but probably reflects the real uncertainty inherent to all abundance determinations based on a prescribed model atmosphere.

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“…Stein & Nordlund 2001;Li et al 2002) and inferring the abundances of various elemental constituents of the sun (e.g. Asplund et al 2005;Caffau et al 2008) are benefitting tremendously from this work: these almost brute force approaches to solar surface convection are offering sufficiently precise information about interior structure to shed light on deeper astrophysical conundrums including the formation scenario of the sun (Guzik & Mussack 2010) and, in combination with solar neutrino observations, standard model physics (Serenelli et al 2009). …”

Section: The Current Framework For Computing Evolutionmentioning

confidence: 99%

Presupernova structure of massive stars

Sukhbold

Arnett

2011

Astrophys Space Sci

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Issues concerning the structure and evolution of core collapse progenitor stars are discussed with an emphasis on interior evolution. We describe a program designed to investigate the transport and mixing processes associated with stellar turbulence, arguably the greatest source of uncertainty in progenitor structure, besides mass loss, at the time of core collapse. An effort to use precision observations of stellar parameters to constrain theoretical modeling is also described.

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The photospheric solar oxygen project

Cited by 267 publications

References 52 publications

The photospheric solar oxygen project

The photospheric solar oxygen project

The solar oxygen abundance from an empirical three-dimensional model

Presupernova structure of massive stars

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