Wolf-Rayet binaries

The configuration of reverse Algol binaries. Because the core-to-envelope mass ratio increases with stellar mass, in very massive binaries above 25 Msun, main-sequence mass transfer can produce stripped donors where the donor remains the more massive component. The following diagram shows the parameter space for the reverse Algol (in blue) and ordinary Algol (in yellow) binary configuration in the initial donor mass-accretor mass plane, for inefficient mass transfer. The parameter space increases with increasing donor masses.

Furthermore, because these stars are close to their Eddington luminosity, the mass donors can be observed as Wolf-Rayet stars on the main sequence. Wolf-Rayet stars are the brightest stars observable in the sky. Their spectra show broad emission lines of hydrogen, helium, nitrogen, oxygen, and/or carbon. They give out strong radiation-driven winds. While most Wolf-Rayet stars are expected to be burning helium in their cores, a handful are also on the main sequence of the Hertzsprung-Russell diagram and are presumably burning hydrogen in their cores. I have identified Wolf-Rayet binaries that are observed counterparts to the reverse Algol binaries, confirming this novel binary evolution channel in which a more massive star can transfer mass to a less massive star on the nuclear timescale. We have obtained multi-epoch spectra of more candidate reverse Algol systems in the Large Magellanic Cloud to get empirical constraints on the surface abundances and wind mass-loss rates of these stars. I am studying the observable properties of this class of binaries to understand their impact on their surroundings and their end products as black holes, as they have much higher wind mass-loss rates than ordinary single stars.