2015AJ....150...62M

WISE J104915.57-531906.1 A+B and WISE J085510.83-071442.5 were recently discovered as the third and fourth closest known systems to the Sun, respectively (2.0 and 2.3 pc). The former consists of a L8+T0.5 binary and the latter is a probable Y dwarf and is the coldest known brown dwarf (∼250 K). We present a search for common proper motion companions to these brown dwarfs using multi-epoch mid-infrared images from the Spitzer Space Telescope. We have also obtained near-infrared adaptive optics (AO) images of WISE J104915.57-531906.1 A+B with the Very Large Telescope to search for companions at smaller separations than reached by Spitzer. No new companions are detected in either system. At projected separations of 25"-420" (50-840 AU) for WISE J104915.57-531906.1 A+B and 4"-420" (9-970 AU) for WISE J085510.83-071442.5, the Spitzer images are sensitive to companions with M_4.5 ≲ 21.6 and 21.9, respectively, which correspond to masses of ≳1 M_Jup for ages of ≥ 1 Gyr and temperatures of ≳150 K. The detection limit in the AO images of WISE J104915.57-531906.1 A + B is ΔH ∼ 10 at 3"-15" (6-30 AU), or ≳7 M_Jup for ≥ 1 Gyr.