The Gaia Ultra-Cool Dwarf Sample - III: Seven new multiple systems containing at least one Gaia DR2 ultra-cool dwarf.

We present ten new ultra-cool dwarfs in seven wide binary systems discovered using Gaia DR2 data, identied as part of our Gaia Ultra-Cool Dwarf Sample project. The seven systems presented here include an L1 companion to the G5 IV star HD 164507, an L1: companion to the V478 Lyr AB system, an L2 companion to the metal-poor K5V star CD-28 8692, an M9V companion to the young variable K0V star LT UMa, and three low-mass binaries consisting of late Ms and early Ls. The HD 164507, CD- 28 8692, V478 Lyr, and LT UMa systems are particularly important benchmarks, because the primaries are well characterised and oer excellent constraints on the atmospheric parameters and ages of the companions. We nd that the M8V star 2MASS J23253550+4608163 is 2.5 mag overluminous compared to M dwarfs of sim- ilar spectral type, but at the same time it does not exhibit obvious peculiarities in its near-infrared spectrum. Its overluminosity cannot be explained by unresolved binarity alone. Finally, we present an L1+L2 system with a projected physical separation of 959 au, making this the widest L+L binary currently known.