Ultra-wide pairs (UWPs) in Taurus and origin of multiplicity

Multiplicity is a key feature in low-mass star-formation. However, its origin is not yet fully understood, even in Taurus that is one of the nearest (145 pc) and best-studied regions. We will present the discovery in Taurus of a new population of ultra-wide pairs (5kAU to 50kAU, hereafter UWPs), (Joncour et al 2017). These UWPs are biased towards higher multiplicity at shorter separation. We suggest that they could be the descendants of the multiple prestellar cores/Class 0 objects and that they may be resulting from a runaway cascade fragmentation of the natal molecular core.