2017MNRAS.468.3499D

Using shape measurement techniques developed for weak lensing surveys, we have identified three new ultracool binaries in the Pan-STARRS 1 (Chambers et al.) survey. Binary companions that are not completely resolved can still alter the shapes of stellar images. These shape distortions can be measured if point spread function 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 arcsec and with flux ratios greater than around 0.1. We then applied our method to a sample of ultracool dwarfs within 30 pc with 293 objects having sufficient Pan-STARRS 1 data for our method. In total, we recovered all but one of the 11 binaries wider than 0.3 arcsec in this sample. Our one failure was a true binary detected with a significant but erroneously high ellipticity that 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/Near Infrared Camera 2 follow-up imaging. This technique will be useful for identifying large numbers of stellar and substellar binaries in the upcoming Large Synoptic Survey Telescope and Dark Energy Survey sky surveys.