  Using shape measurement techniques developed for weak lensing surveys we have
identified three new ultracool binaries in the Pan-STARRS1 survey. Binary
companions which are not completely resolved can still alter the shapes of
stellar images. These shape distortions can be measured if PSF anisotropy
caused by the telescope is properly accounted for. We show using both a sample
of known binary stars and simulated binaries that we can reliably recover
binaries wider than around 0.3" and with flux ratios greater than around 0.1.
We then applied our method to a sample of ultracool dwarfs within 30pc with 293
objects having sufficient Pan-STARRS1 data for our method. In total we
recovered all but one of the 11 binaries wider than 0.3" in this sample. Our
one failure was a true binary detected with a significant but erroneously high
ellipticity which led it to be rejected in our analysis. We identify three new
binaries, one a simultaneous discovery, with primary spectral types M6.5, L1
and T0.5. These latter two were confirmed with Keck/NIRC2 follow-up imaging.
This technique will be useful for identifying large numbers of stellar and
substellar binaries in the upcoming LSST and DES sky surveys.
