On the detection of two new trans-Neptunian binaries from the CFEPS Kuiper belt survey

We report here the discovery of new near-equal-mass trans-Neptunian Binary (TNB) L5c02 and the the putative detection of a second TNB (L4k12) among the detections in the second and third years of the Canada-France Ecliptic Plane Survey (CFEPS). These new binaries (internal designations L4k12 and L5c02) have moderate separations of 0.4″ and 0.6″, respectively. The follow-up observation confirmed the binarity of L5c02, but L4k12 still lacks follow-up observations. L4k12 has a heliocentric orbital inclination of ∼35°, marking this system as having the highest heliocentric orbital inclination among known near-equal-mass binaries. Both systems are members of the classical main Kuiper belt population. Based on the sample of objects searched, we determine that the fraction of near-equal-mass wide binaries with separations >0.4″ is 1.5% to 20% in the cold main classical Kuiper belt, and if our detection of the binarity L4k12 holds, 3% to 43% in the hot main classical objects are binary. In this article we describe our detection process, the sample of objects surveyed, and our confirmation observations.