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 transNeptunian object.

The Complex Rotational Light Curve of (385446) Manwë–Thorondor, a Multicomponent Eclipsing System in the Kuiper Belt

“…With the rotation period we measure for Manwë (P = 11.88 h), this requires r = 0.80 g/cm 3 . This density value is near the nominal value measured for KBOs of comparable size (Stansberry et al 2008), near the value (0.75 g/cm 3 ) estimated by Grundy et al (2014) for the combined system bulk density, and within the range of values estimated for other likely contact binaries (Thirouin & Sheppard 2017, 2018. Hence, this shape model is a good starting point for modeling Manwë's light curve.…”

The color and binarity of (486958) 2014 MU69 and other long-range New Horizons Kuiper Belt targets

“…The physical interpretation of large variations among small objects is preferably attributed to object elongation rather than albedo patches (Trilling et al 2006) since mechanisms for large albedo variations are not highly plausible for objects of this size range. Some of these objects could be close or contact binaries (Benecchi & Sheppard 2013;Thirouin & Sheppard 2017), however, work by Thirouin & Sheppard (2018a,b) suggest a lower contact binary fraction among the CC population (10%) than has been found for other dynamical regions of the Kuiper Belt (eg. Resonant objects 40-50%).…”

Great Expectations: Plans and Predictions for New Horizons Encounter With Kuiper Belt Object 2014 MU69 (“Ultima Thule”)

“…Results of the 17 July 2017 stellar occultation by Ultima indicate that this object displays a very irregular shape and could even be a close or contact binary (Buie et al, , ; Zangari et al, ). Binaries are common in the Kuiper Belt (Noll et al, ), including contact binaries (Lacerda, ; Lacerda et al, ; Thirouin et al, ; Thirouin & Sheppard, ), and it has been argued that many short period comets, such as 67P/Churyumov‐Gerasimenko, 8P/Tuttle, and 103P/Hartley 2, and even 19P/Borrely and 1P/Halley, were formed as or evolved to be contact binaries (or more generally, bilobate bodies; Harmon et al, ; Nesvorný et al, ; Rickman et al, ), albeit from smaller components than the ostensible components of Ultima. Gravitational collapse of “pebble clouds” in the solar nebula is predicted to have naturally and efficiently formed binaries in the Kuiper belt, and with subequal mass ratios (Nesvorný et al, ).…”