Gaia wide binaries

The public catalogue contains, after removal of clusters and resolved higher order multiples, >50000MS/MS, >3000WD/MS, and nearly 400WD/WD binaries with projected separations of 50<~s/au<50000. Accounting for incompleteness and selection effects, we model the separation distribution of each class of binaries as a broken power law, revealing marked differences between the three populations.

The separation distribution of MS/MS systems is nearly consistent with a single power law of slope -1.6 over at least 500<s/au<50000, with marginal steepening at s>10000au. In contrast, the separation distributions of WD/MS and WD/WD binaries show distinct breaks at ~3000 and ~1500au, respectively: they are flatter than the MS/MS distribution at small separations and steeper at large separations. Using binary population synthesis models, we show that these breaks are unlikely to be caused by external factors but can be explained if the WDs incur a kick of ~0.75km/s during their formation, presumably due to asymmetric mass-loss.