  We study the cosmological evolution of a tachyon scalar field T with a Dirac-
Born- Infeld type lagrangian and potential V (T) coupled to a canonically
normalized scalar field with an arbitrary but factorizeable interaction
potential B (T,phi) in the presence of a barotropic fluid. We will assume that
the force between the barotropic fluid and the scalar field is only
gravitational and we show that all models dependence is given in terms of three
parameters: L1= -V_T/V, L2= -B_T/B and L3= -B_phi/B which are field and time
dependent. We give the general solution to the cosmological equations of motion
and determine in which cases we can have an accelerating universe giving rise
to dark energy.
