Self-consistent modeling of mass transfer and stellar evolution in eccentric binary star systems.

A majority of massive binaries will interact with a companion through Roche-lobe overflow mass transfer, impacting their component masses, orbit, and ultimate fate of the binary. Modern stellar evolution codes such as MESA can simulate mass transfer while evolving stars simultaneously where the orbit is often assumed to be circular. However observations of semi-detached binaries suggest systems can undergo mass transfer while in eccentric orbits, and remain eccentric after mass transfer episodes. We employ analytic equations for the secular orbital evolution of a binary under eccentric mass transfer into MESA, investigating binaries containing a compact object and star with a range of masses and orbital configurations. We find regions of parameter space where the orbital evolution due to eccentric mass transfer diverges significantly from the circular case, highlighting the need for more studies in this regime.