  In the present work we study a dark energy model in which a non-linear scalar
field (tachyon) with a Born-Infeld type of action is responsible for the
observed cosmic acceleration. The potential of the tachyon is well-motivated
since it comes from open string theory and the model is subjected to various
cosmological constraints with data coming from supernovae as well as from
microwave background radiation. Our analysis shows that in the particular model
under study the tachyon can be an excellent candidate for dark energy in the
universe, as the model agrees with a series of observational data and for a
wide range of the parameters of the model.
