The carbon Cepheid RT Trianguli Australis: additional evidence of triple-α and CNO cycling |
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| Authors: | George Wallerstein † Sean Matt† Guillermo Gonzalez† |
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| Institution: | Astronomy Department, University of Washington, Box 351580, Seattle, WA 98195, USA |
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| Abstract: | We have used echelle spectra of resolving power 35 000 to derive chemical abundances and the 12C/13C ratio in the 1.9-d carbon Cepheid RT TrA and the Cepheid U TrA, employed as a comparison star. We confirm that RT TrA is very metal-rich with Fe/H]=+0.4. In addition, C and N are substantially in excess, and a small deficiency in O is present. We interpret these anomalies as resulting from the appearance on the stellar surface of material enriched in 12C by the 3- α process, followed by CNO cycling to convert 12C to 13C and 14N. In addition, some 16O has been processed to 14N. The partial processing of 16O to 14N indicates that substantial 17O may be present. Proton capture seems to have enhanced 23Na from the Ne isotopes. |
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| Keywords: | stars: abundances stars: chemically peculiar stars: individual: RT TrA stars: individual: U TrA stars: Population II Cepheids |
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