A peculiar metal-rich star, HD 135485 |
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Authors: | C. Trundle P.L. Dufton W.R.J. Rolleston R.S.I. Ryans D.J. Lennon N. Lehner |
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Affiliation: | 1Department of Pure and Applied Physics, The Queen's University, Belfast BT7 1NN;2ING Telescopes, Apartado do Correos 368, Santa Cruz De La Palma 38780, Canary Islands, Spain;3Department of Physics and Astronomy, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA |
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Abstract: | Local thermodynamic equilibrium (LTE) absolute and differential abundances are presented for a peculiar metal-rich B-type star, HD 135485. These suggest that HD 135485 has a general enrichment of ∼0.5 dex in all the metals observed (C, N, O, Ne, Mg, Al, Si, P, S, Cl, Ar, Sc, Ti, Cr, Mn, Fe and Sr), except for nickel. The helium enhancement and hence hydrogen deficiency can account for ≤ 0.2 dex of this enhancement of metals, with the additional enhancement probably being representative of the progenitor gas. However, some of the metals appear to have greater enhancements, which may have occurred during the star's evolution. The significantly larger nitrogen abundance coupled with a modest helium enhancement observed in HD 135485 indicates that carbon–nitrogen (CN) processed material has possibly contaminated the stellar surface. Neon and carbon enhancements may indicate that helium core flashes have also occurred in HD 135485. Some of the iron-group elements (viz. Mn and Ni) appear to have similar abundance patterns to that of silicon Ap stars, but it is uncertain how these abundance patterns formed if they were not present in the progenitor gas. From a kinematical investigation it is unclear whether this star formed in a metal-rich region as implied by its chemical composition. From its position in the Hertzsprung–Russell diagram, HD 135485 would appear to be an evolved star lying close to or on the horizontal branch. |
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Keywords: | stars: abundances stars: atmospheres stars: early-type stars: individual: HD 135485 |
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