Numerical Simulations of Gamma-Ray Emitting Binary Systems
Ralf Kissmann, David Huber, Olaf Reimer, and Anita Reimer
Observations show that there are several binary systems within our Galaxy that emit high-energy or even very-high-energy gamma radiation. Two types of such systems have been detected: on the one hand there are colliding-wind binaries, systems that contain two early-type stars where gamma-rays are produced by high-energy particles accelerated at the collision region of the massive stellar winds. Of these, only two gamma-ray emitting systems have been detected so far (Eta Carinae and γ² Velorum), whereas earlier theoretical models expected a multitude of such systems to be observable with currently available detectors. On the other hand there is the class of gamma-ray binaries: binary systems of an early-type star and a compact object, which emit the majority of their radiative power in the gamma-ray regime. For these systems there are two commonly accepted models: gamma-ray emission related to a relativistic jet outflow from the compact object (microquasar scenario) or acceleration of high-energy particles by the interaction of a pulsar wind with the stellar wind of the early-type star (pulsar scenario). We study these systems via (magneto-)hydrodynamical simulations of the stellar winds together with a combined solution of the trans- port equation of the energetic particles accelerated at the shock waves. With this, we can model colliding-wind binary systems and gamma-ray binaries in the pulsar scenario. We show results of these modelling efforts, where we study the dynamics of the systems and, in particular, their time-variable gamma-ray emission.