Change in the Orbital Period of a Binary System Due to an Outburst in a Windy Accretion Disk

Abstract

Abstract: We consider a new mechanism for the removal of 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 disk. A powerful wind from a disk is observed in X-ray transients and is predicted by models. We have obtained an analytical estimate for the increase in the orbital period of a binary system with a wind from the disk during an outburst; quantitative estimates are given for the systems XTE J1118+480, A0620-00, and GRS 1124-68. The rates of increase in the period are comparable in absolute value to the observed rates of secular decrease in the period. We also compare the predicted rates of change in the period of a binary system due to the mass transfer into the disk and the outflow from the second Lagrange point with the observed ones. We conclude that the above-mentioned mechanisms cannot explain the observed secular decrease in the period, and it is necessary to consider a circumbinary disk that removes the binary’s angular momentum.