An analytic model for interacting dark energy and its observational   constraints
  The paper deals with a theoretical model for interacting dark energy. The interaction between the cold dark matter (dust) and the dark energy has been assumed to be non-gravitational in nature. Exact analytic cosmological solutions are obtained both for constant and variable equation of state for dark energy. It is found that, for very small value of the coupling parameter (in the interaction term), the model asymptotically extends up to $\Lambda$CDM, while the model can enter into the phantom domain asymptotically, if the coupling parameter is not so small. Both the solutions are then analyzed with 194 Supernovae Type Ia data. The best fit parameters are shown with 1$\sigma$ and 2$\sigma$ confidence intervals. Finally, we have discussed the cosmographic parameters for both the cases. 
Supriya Pan, Subhra Bhattacharya, and Subenoy Chakraborty
gr-qc