Transient Crossing of Phantom divide line $w_{\mathrm{\Lambda }}=-1$ under Gauss-Bonnet interaction

Smooth double crossing of the phantom barrier $w_{\mathrm{\Lambda }}=-1$ has been found possible in cosmological model with Gauss-Bonnet-scalar interaction, in the presence of background cold dark matter. Such crossing has been observed to be a sufficiently late time phenomena and independent of the sign of Gauss-Bonnet-scalar interaction. The luminosity distance versus redshift curve shows a perfect fit with the $\mathrm{\Lambda }CDM$ model up to $z=3.5$.