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

Autor(es)

Kiselman, D. ^{[1, 2]} ; Pereira, T. M. D. ^[3] ; Gustafsson, B. ^{[4, 5]} ; Asplund, M. ^{[3, 6]} ; Melendez, J. ^[7] ; Langhans, K. ^{[1, 2]}

Afiliação do(s) autor(es)

^[1] AlbaNova Univ Ctr, Royal Swedish Acad Sci, Inst Solar Phys, S-10691 Stockholm - Sweden

^[2] Stockholm Univ, AlbaNova Univ Ctr, Stockholm Observ, Dept Astron, S-10691 Stockholm - Sweden

^[3] Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611 - Australia

^[4] Uppsala Univ, Dept Phys & Astron, S-75120 Uppsala - Sweden

^[5] AlbaNova Univ Ctr, S-10691 Stockholm - Sweden

^[6] Max Planck Inst Astrophys, D-85741 Garching B Munchen - Germany

^[7] Univ Sao Paulo, Dept Astron IAG USP, BR-05508900 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Astronomy & Astrophysics; v. 535, NOV 2011.
• Citações Web of Science: 25

Resumo

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 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 degrees. 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 similar to 45 degrees 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. (AU)

• Processo FAPESP: 10/17510-3 - Influência da formação de planetas na composição química de estrelas do tipo solar
• Beneficiário: Jorge Luis Melendez Moreno
• Linha de fomento: Auxílio à Pesquisa - Regular