2017ApJ...837L..19C

Some short-period, detached binary systems have recently been reported as experiencing very rapid orbital decay, much faster than is expected from the angular-momentum loss caused by gravitational radiation alone. As these systems contain fully convective stars, magnetic braking is not believed to be operative, making the large orbital-period derivative puzzling. Here, we explore whether a resonant interaction between the binary and a surrounding circumbinary (CB) disk could account for the observed orbital decay. Our calculations indicate that the observed orbital-period derivatives in seven detached binaries can be produced by the resonant interaction between the binary and a CB disk if the latter has a mass in the range of 10^–4–10^–2 M_☉, which is of the same order as the inferred disk mass (∼2.4×10^–4 M_☉) in the post-common-envelope binary NN Ser.