An analysis of the Eris (2003 UB313) light curve

Having recently reported in Carraro et al. [2006. Astron. Astrophys. 460, L39] on the first light curve of the dwarf planet Eris (2003 UB313), we address here with more details the issue of the significance of the variability we found, and speculate on the possible origin of it. We present additional tests with respect to the quoted paper, making the variability detection more solid. Moreover, we discuss with more emphasis the possible role of Dysnomea, the recently discovered Eris satellite. We suggest that the presence of the satellite is not sufficient to account for the luminosity variation of Eris and propose other possible scenarios. At last we suggest the possibility to investigate the role of tidal interactions between Eris and Dysnomea.