The Plutino population: An Abundance of contact binaries

Abstract

We observed twelve Plutinos over two separated years with the 4.3m Lowell's Discovery Channel Telescope. Here, we present the first lightcurve data for those objects. Three of them (2014JL$_{80}$, 2014JO$_{80}$, 2014JQ$_{80}$) display a large lightcurve amplitude explainable by a single elongated object, but are most likely caused by a contact binary system due to their lightcurves morphology. These potential contact binaries have rotational periods from 6.3h to 34.9h and peak-to-peak lightcurve variability between 0.6 and 0.8mag. We present partial lightcurves allowing us to constrain the lightcurve amplitude and the rotational period of another nine Plutinos. By merging our data with the literature, we estimate that up to $\sim$40$\%$ of the Plutinos could be contact binaries. Interestingly, we found that all the suspected contact binaries in the 3:2 resonance are small with absolute magnitude H$>$6mag. Based on our sample and the literature, up to $\sim$50$\%$ of the small Plutinos are potential contact binaries.