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Line formation in solar granulation VII. CO lines and the solar C and O isotopic abundances

Scott, Patrick; Asplund, Martin; Grevesse, N; Sauval, A J

Description

CO spectral line formation in the Sun has long been a source of consternation for solar physicists, as have the elemental abundances it seems to imply. We modelled solar CO line formation using a realistic, ab initio, time-dependent 3D radiative-hydrodynamic model atmosphere. Results were compared with space-based observations from the ATMOS space shuttle experiment. We employed weak12C16O,13C16O and12C18O lines from the fundamental (Δv = 1) and first overtone (Au = 2) bands to determine the...[Show more]

dc.contributor.authorScott, Patrick
dc.contributor.authorAsplund, Martin
dc.contributor.authorGrevesse, N
dc.contributor.authorSauval, A J
dc.date.accessioned2015-12-07T22:52:47Z
dc.date.available2015-12-07T22:52:47Z
dc.identifier.issn0004-6361
dc.identifier.urihttp://hdl.handle.net/1885/27577
dc.description.abstractCO spectral line formation in the Sun has long been a source of consternation for solar physicists, as have the elemental abundances it seems to imply. We modelled solar CO line formation using a realistic, ab initio, time-dependent 3D radiative-hydrodynamic model atmosphere. Results were compared with space-based observations from the ATMOS space shuttle experiment. We employed weak12C16O,13C16O and12C18O lines from the fundamental (Δv = 1) and first overtone (Au = 2) bands to determine the solar carbon abundance, as well as the12C/13C and16O/18O isotopic ratios. A weighted solar carbon abundance of log εC = 8.39 ± 0.05 was found. We note with satisfaction that the derived abundance is identical to our recent 3D determination based on C I, [C I], C2 and CH lines, increasing our confidence in the accuracy of both results. Identical calculations were carried out using ID models, but only the 3D model was able to produce abundance agreement between different CO lines and the other atomic and molecular diagnostics. Solar12C/13C and16O/18O ratios were measured as 86.8-3.7+3.9 (δ13C = 30-44+46) and 479-28+29 (δ18O = 41-59+67), respectively. These values may require current theories of solar system formation, such as the CO self-shielding hypothesis, to be revised. Excellent agreement was seen between observed and predicted weak CO line shapes, without invoking micro- or macroturbulence. Agreement breaks down for the strongest CO lines however, which are formed in very high atmospheric layers. Whilst the line asymmetries (bisectors) were reasonably well reproduced, line strengths predicted on the basis of C and O abundances from other diagnostics were weaker than observed. The simplest explanation is that temperatures are overestimated in the highest layers of the 3D simulation. Thus, our analysis supports the presence of a COmosphere above the traditional photospheric temperature minimum, with an average temperature of less than 4000 K. This shortcoming of the 3D model atmosphere is not surprising, given that it was never intended to properly describe such high layers.
dc.publisherSpringer
dc.sourceAstronomy and Astrophysics
dc.subjectKeywords: Computer simulation; Heat convection; Hydrodynamics; Infrared radiation; Solar radiation; Solar system; Line: profiles; Solar system: formation; Sun: abundances; Sun: infrared; Sun: photosphere; Astrophysics Convection; Line: profiles; Solar system: formation; Sun: abundances; Sun: infrared; Sun: photosphere
dc.titleLine formation in solar granulation VII. CO lines and the solar C and O isotopic abundances
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume456
dc.date.issued2006
local.identifier.absfor020110 - Stellar Astronomy and Planetary Systems
local.identifier.ariespublicationu4114753xPUB52
local.type.statusPublished Version
local.contributor.affiliationScott, Patrick, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationAsplund, Martin, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationGrevesse, N, Universite de Liege
local.contributor.affiliationSauval, A J, Observatoire Royal de Belgique
local.bibliographicCitation.startpage675
local.bibliographicCitation.lastpage688
local.identifier.doi10.1051/0004-6361:20064986
dc.date.updated2015-12-07T12:32:53Z
local.identifier.scopusID2-s2.0-33748759313
CollectionsANU Research Publications

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