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Is the solar spectrum latitude-dependent? An investigation with SST/TRIPPEL

Kiselman, D; Pereira, Tiago; Gustafsson, Bengt; Asplund, Martin; Melendez, Jorge; Langhans, K

Description

Context. In studies of the solar spectrum compared to spectra of solar twin stars, it has been found that the chemical composition of the Sun seems to depart systematically from those of the twins. One possible explanation could be that the effect is caused by the special aspect angle of the Sun when observed from Earth compared with the aspect angles of the twins. This means that a latitude dependence of the solar spectrum, even with the heliocentric angle constant, could lead to the observed...[Show more]

dc.contributor.authorKiselman, D
dc.contributor.authorPereira, Tiago
dc.contributor.authorGustafsson, Bengt
dc.contributor.authorAsplund, Martin
dc.contributor.authorMelendez, Jorge
dc.contributor.authorLanghans, K
dc.date.accessioned2015-12-10T21:54:27Z
dc.identifier.issn0004-6361
dc.identifier.urihttp://hdl.handle.net/1885/38946
dc.description.abstractContext. In studies of the solar spectrum compared to spectra of solar twin stars, it has been found that the chemical composition of the Sun seems to depart systematically from those of the twins. One possible explanation could be that the effect is caused by the special aspect angle of the Sun when observed from Earth compared with the aspect angles of the twins. This means that a latitude dependence of the solar spectrum, even with the heliocentric angle constant, could lead to the observed effects. Aims. We explore a possible variation in the strength of certain spectral lines that are used in the comparisons between the composition of the Sun and the twins at loci on the solar disk with different latitudes but at constant heliocentric angle. Methods. We use the TRIPPEL spectrograph at the Swedish 1-m Solar Telescope on La Palma to record spectra in five spectral regions to compare different locations on the solar disk at a heliocentric angle of 45°. Equivalent widths and other parameters are measured for fifteen different lines representing nine atomic species. Spectra acquired at different times are used in averaging the line parameters for each line and observing position. Results. The relative variations in equivalent widths at the equator and at solar latitude ∼45° are found to be less than 1.5% for all spectral lines studied. Translated into elemental abundances as they would be measured from a terrestrial and a hypothetical pole-on observer, the difference is estimated to be within 0.005 dex in all cases. Conclusions. It is very unlikely that latitude effects could cause the reported abundance difference between the Sun and the solar twins. The accuracy obtainable in measurements of small differences in spectral line strengths between different solar disk positions is very high, and can be exploited in studies of, e.g. weak magnetic fields or effects of solar activity on atmospheric structure.
dc.publisherSpringer
dc.rightsAuthor/s retain copyright
dc.sourceAstronomy and Astrophysics
dc.subjectKeywords: Aspect angles; Atomic species; Chemical compositions; Composition of the Sun; Elemental abundance; Equivalent width; Instrumentation: spectrographs; Latitude effects; Line parameters; Line: formation; Solar activity; Solar disk; Solar spectrum; Solar tele Instrumentation: spectrographs; Line: formation; Stars: abundances; Sun: abundances
dc.titleIs the solar spectrum latitude-dependent? An investigation with SST/TRIPPEL
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume535
dc.date.issued2011
local.identifier.absfor020110 - Stellar Astronomy and Planetary Systems
local.identifier.ariespublicationu3356449xPUB169
local.type.statusPublished Version
local.contributor.affiliationKiselman, D, Royal Swedish Academy of Sciences
local.contributor.affiliationPereira, Tiago, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationGustafsson, Bengt, Uppsala Astronomical Observatory
local.contributor.affiliationAsplund, Martin, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationMelendez, Jorge, University of Sao Paulo
local.contributor.affiliationLanghans, K, Royal Swedish Academy of Sciences
local.bibliographicCitation.startpageA14
local.bibliographicCitation.lastpage9
local.identifier.doi10.1051/0004-6361/201117553
local.identifier.absseo970102 - Expanding Knowledge in the Physical Sciences
dc.date.updated2016-02-24T09:54:03Z
local.identifier.scopusID2-s2.0-80055013143
local.identifier.thomsonID000297841200026
dcterms.accessRightsOpen Access
CollectionsANU Research Publications

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