engleski

Probing the Models: V380 Cygni Revisited

The eclipsing and double-lined spectroscopic binary V380 Cyg is an extremely important probe of stellar evolution: its primary component is a high-mass star at the brink of leaving the main sequence whereas the secondary star is still in the early part of its main sequence lifetime. We present extensive high-resolution echelle and grating spectrsocopy from Ondrejov, Calar Alto, Victoria and La Palma. We apply spectral disentangling to unveil the individual spectra of the two stars and obtain new spectroscopic elements. We perform a detailed abundance analysis by fitting non-LTE theoretical line profiles to the disentangled spectrum of the evolved primary star, and reveal an elemental abundance pattern reminiscent of a tzpical nearby B star. Contrary to the predictions of recent theoretical evolution models with rotational mixing, no trace of abundance modifications due to the CNO cycle are detected. No match can be found between the predictions of these models and the porperties of the primary star: a mass discrepancy of 1.5 M_sun exists and remain unexplained.

binary stars; stellar models; chemical composition

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