Atmospheric chemical composition of the "twin" components of equal mass inthe CPSB2 system 66 Eri

We determine the atmospheric chemical composition of the components of the CP SB2 system 66 Eri with approximately equal masses (M-A/M-B = 0.97) by us ing two CCD echelle spectra of the star. These spectra have been taken with the 1-m telescope at Special Astrophysical Observatory with a spectral res olution of 36000 and a signal-to-noise ratio no less than 100 in the wavele ngth range 4385-6695 Angstrom. The model-atmosphere parameters for the comp onents are estimated by analyzing all available photometric and spectrophot ometric data and the equivalent widths of iron lines. For components A and B, we have obtained T-effA = 11 100 K, T-effB = 10900 K, log g(A) = 4.25, l og g(B) = 4.25, V-turbA = 0.9 km s(-1), V-turbB = 0.7 km s(-1), and Vsini(A ,B) = 17 km s(-1). The derived projected rotational velocities of the compo nents, together with the HIPPARCOS parallax and photometric observations, s how that their rotation may he synchronized with the orbital period. The st ar exhibits a considerable infrared excess at wavelengths longer than 25 mu m. The synthetic-spectrum and model-atmosphere methods are used to determi ne the atmospheric abundances of 26 chemical elements in component B and 15 chemical elements in components. The components differ markedly in chemica l composition. The peculiar component B exhibits no chemical anomalies that are typical of the Hg-Mn group, such as an underabundance of He and Al and an enhancement of P and Ga, but shows large heavy-element overabundances r eaching 4-5 dex. The atmosphere of component A also exhibits moderate overa bundances of Mn and Ba, but no lines of other heavy elements have been foun d in its spectrum. However, an estimate of the upper limit on their abundan ces does no rule out small heavy-element overabundances in the atmosphere o f component A either. 66 Eri is the first and the only close SB2 system wit h CP non-Hg-Mn components studied to date.