Change in the orbital period of a binary system due to an outburst in a windy accretion disc

TL;DR

This paper investigates how wind-driven mass loss from accretion discs in X-ray binaries affects their orbital periods, providing analytical estimates and comparing with observations, concluding additional mechanisms are needed to explain observed period changes.

Contribution

It introduces a new analytical model for orbital period change due to disc winds during outbursts in X-ray binaries and compares predictions with observed data.

Findings

Wind-driven mass loss can cause orbital period increase during outbursts.

Predicted period change rates are comparable to observed secular decreases.

Additional mechanisms like circumbinary discs are needed to fully explain observations.

Abstract

We consider a new mechanism for the removal of the angular momentum from an X-ray binary system and the change in its orbital period - the mass loss in the form of a wind from an accretion disc. Both observations and models predict powerful winds from discs in X-ray transients. We have obtained an analytical estimate for the increase in the orbital period of a binary system with a wind from the disc during an outburst, and quantitative estimates are given for the systems XTE J1118+480, A0620-00 and GRS 1124-68. Resulting rate of period grow is of order of the observed rates of secular decrease in the period. We also compare the predicted rate of change in the period of a binary system due to the flow of matter into the disc and outflow from the second Lagrange point with the observations. It is concluded that the above mechanisms cannot explain the observed secular decrease in the period of the three X-ray Novae, and it is necessary to consider a circumbinary disc that drains the binary's angular momentum.