A possible dynamically Cold Classical contact binary: (126719) 2002 CC249

Abstract

Images of the Kuiper belt object (126719) 2002 CC 249 obtained in 2016 and 2017 using the 6.5m Magellan-Baade Telescope and the 4.3m Discovery Channel Telescope are presented. A lightcurve with a periodicity of 11.87±0.01 h and a peak-to-peak amplitude of 0.79±0.04 mag is reported. This high amplitude double-peaked lightcurve can be due to a single elongated body, but it is best explained by a contact binary system from its U-/V-shaped lightcurve. We present a simple full-width-at-half-maximum (FWHM) test that can be used to determine if an object is likely a contact binary or an elongated object based on its lightcurve. Considering that 2002 CC 249 is in hydrostatic equilibrium, a system with a mass ratio q min =0.6, and a density ρ min =1 g cm 3 , or less plausible a system with q max =1, and ρ max =5 g cm 3 can interpret the lightcurve. Assuming a single Jacobi ellipsoid in hydrostatic equilibrium, and an equatorial view, we estimate ρ≥0.34 g cm −3 , and a/b=2.07. Finally, we report a new color study showing that 2002 CC 249 displays an ultra red surface characteristic of a dynamically Cold Classical trans-Neptunian object.