tachyonic teleparallel dark energy

teleparallel gravity is an equivalent formulation of general relativity in which instead of the ricci scalar r, one uses the torsion scalar t for the lagrangian density. recently teleparallel dark energy has been proposed by geng et al. (in phys. lett. b 704, 384, 2011). they have added quintessence scalar field, allowing also a non-minimal coupling with gravity in the lagrangian of teleparallel gravity and found that such a non-minimally coupled quintessence theory has a richer structure than the same one in the frame work of general relativity. in the present work we are interested in tachyonic teleparallel dark energy in which scalar field is responsible for dark energy in the frame work of torsion gravity. we find that such a non-minimally coupled tachyon gravity can realize the crossing of the phantom divide line for the effective equation of state. using the numerical calculations we display such a behavior of the model explicitly.