Gamma-ray binaries: Stable mass transfer from a neutron star to a black hole

Gamma-ray bursts are characterized by a duration of milliseconds to several minutes in which an enormous amount of radiation is emitted. The origin of these phenomena is still unknown because proposed models fail to explain all of the observed features. Our proposed solution to this conundrum is a new class of mass-exchanging binaries in which a neutron star transfers mass to a black hole. According to recent studies, binaries that contain a neutron star and a black hole are much more frequent than was previously believed. Mass exchange is driven by the emission of gravitational waves, but the redistribution of mass in the binary system prevents coalescence. The phase of mass transfer is surprisingly stable and lasts for several thousands of orbital revolutions (about a minute). With a simple analytic model, we demonstrated that this new class of binaries could provide an excellent candidate for the observed phenomena known as gamma-ray bursts.