Constraints on the common-envelope evolution process from wide triple systems

Common envelope (CE) is an important phase in the evolution of interacting binary systems. The interaction of the binary components during the CE evolution (CEE) stage gives rise to orbital inspiral and the formation of a short-period binary or a merger, on the expense of extending and/or ejecting the envelope. CEE is not well understood, as hydrodynamical simulations show that only a fraction of the CE mass is ejected during the dynamical inspiral, in contrast with observations of post-CE binaries. We propose a novel method for constraining the mass-loss time-scale of the CE, using post-CE binaries which are part of wide-orbit triple systems. The orbit/existence of a third companion constrains the CE mass-loss time-scale, since rapid CE mass-loss may disrupt the triple system, while slower CE mass-loss may change the orbit of the third companion without disrupting it. As first test cases we examine two observed post-CE binaries in wide triples, Wolf 1130 and GD 319. We follow their evolution due to mass-loss using analytic and numerical tools, and consider different mass-loss functions. We calculate a wide grid of binary parameters and mass-loss time-scales in order to determine the most probable mass-loss time-scale leading to the observed properties of the systems. We find that mass-loss time-scales of the order of 10 3 -10 5 yr are the most likely to explain these systems. Such long time-scales are in tension with most of the CE mass-loss models, which predict dynamical time-scales, but are potentially consistent with the longer time-scales expected from the dust-driven winds model for CE ejection.