Effects of time-varying β in SNLS3 on constraining interacting dark energy models

It has been found that, for the Supernova Legacy Survey three-year (SNLS3) data, there is strong evidence for the redshift evolution of the color-luminosity parameter beta. In this paper, adopting the omega-cold-dark-matter (omega CDM) model and considering its interacting extensions (with three kinds of interaction between dark sectors), we explore the evolution of beta and its effects on parameter estimation. In addition to the SNLS3 data, we also use the latest Planck distance priors data, the galaxy clustering data extracted from sloan digital sky survey data release 7 and baryon oscillation spectroscopic survey, as well as the direct measurement of Hubble constant H-0 from the Hubble Space Telescope observation. We find that, for all the interacting dark energy (IDE) models, adding a parameter of beta can reduce chi 2 by similar to 34, indicating that a constant beta is ruled out at 5.8 sigma confidence level. Furthermore, it is found that varying beta can significantly change the fitting results of various cosmological parameters: for all the dark energy models considered in this paper, varying beta yields a larger fractional CDM densities Omega(c0) and a larger equation of state omega; on the other side, varying beta yields a smaller reduced Hubble constant h for the omega CDMmodel, but it has no impact on h for the three IDE models. This implies that there is a degeneracy between h and coupling parameter gamma. Our work shows that the evolution of beta is insensitive to the interaction between dark sectors, and then highlights the importance of considering beta is evolution in the cosmology fits.