Confirming new white dwarf-ultracool dwarf binary candidates
  We present the results of a study to discover prospective new white dwarf-L
dwarf binaries as identified by their near-infrared excesses in the UKIDSS
catalogue. We obtained optical spectra to validate the white dwarf nature for
22 of the candidate primary stars, confirming ten as white dwarfs and
determining their effective temperatures and gravities. For all ten white
dwarfs we determined that the near-infrared excess was indeed indicative of a
cool companion. Six of these are suggestive of late M dwarf companions, and
three are candidate L dwarf companions, with one straddling the M$-$L boundary.
We also present near-infrared spectra of eight additional candidate white
dwarf-ultracool dwarf binaries where the white dwarf primary had been
previously confirmed. These spectra indicate one candidate at the M$-$L
boundary, three potential L dwarf companions, and one suspected M dwarf, which
showed photometric variability on a $\sim$6 hour period, suggesting the system
may be close. Radial velocity follow up is required to confirm whether these
systems are close, or widely separated.
