The spectrum of the SB2 HD 64491 and the problem of metal abundances in (lambda) Boo stars

The spectrum of the classical (lambda) Boo star HD 64491 reveals that the object is a double-lined spectroscopic binary whose components have different v sin i values. From such a tangled spectrum, we show that large metal underabundances can be derived with the hypothesis that the spectrum is formed by a single object, while the abundance peculiarities are drastically reduced when the duplicity is taken into account.