Wide Binaries in the Orion Nebula Cluster

Abstract

With the purpose of identifying a group of wide binaries in a very young cluster (T ≤ 10⁶ years) and of getting a closer look at the “primaeval” distribution of separations, we have conducted a search for common proper motion companions among the nearest neighbor of each one of the Orion Nebula Cluster stars, for which Jones-Walker have determined proper motions. Each one of these pairs was subjected to a selection procedure in order to obtain a sample with a high expectation of them being physical systems. We have identified 68 such pairs of stars with projected separations between 2000 and 33 000 astronomical units. The distribution of separations f(s) seems to be Oepik-like, i.e. f(s)ds ~ds/s.