Neon and oxygen in low activity stars: towards a coronal unification with the Sun
| Autor: | Robrade, J., Schmitt, J. H. M. M., Favata, F. |
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| Rok vydání: | 2008 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1051/0004-6361:200809690 |
| Popis: | The disagreement between helioseismology and a recent downward revision of solar abundances has resulted in a controversy about the true neon abundance of the Sun and other stars. We investigated XMM-Newton and Chandra high-resolution X-ray spectra of weakly and moderately active stars (log L_x/L_bol = -5...-7) and determined their coronal Ne/O abundance ratio by using two linear combinations of strong emission lines as well as a global-fitting method. The sample stars show a correlation between their Ne/O ratio and stellar activity in the sense that stars with a higher activity level show a higher Ne/O ratio. We find that the Ne/O ratio decreases in our sample from values of Ne/O~0.4 down to Ne/O~0.2, suggesting that ratios similar to 'classical' solar values are rather common for low activity stars. A significantly enhanced neon abundance as the solution to the solar modeling problem seems unlikely. We find no indications of a peculiar position of the Sun among other stars. Comment: Accepted for publication in A&A, 8 pages, 5 figures |
| Databáze: | arXiv |
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