Red giant depletion in globular cluster cores

We investigate the observed depletion of red giants in the cores of post-core-collapse globular clusters. In particular, the evolutionary scenario we consider is a binary consisting of two low-mass stars which undergoes two common-envelope phases. The first common-envelope phase occurs when the primary is a red giant resulting in a helium white dwarf and main-sequence star in a detached binary. The second common-envelope phase occurs shortly after the secondary becomes a red giant. During the second common-envelope phase, the degenerate helium cores merge resulting in a core mass greater than the helium burning limit and the formation of a horizontal branch star. We show that stellar encounters enhance this evolutionary route in post-core-collapse clusters. These encounters increase the population of binary secondaries which would have evolved on to the red giant branch in the recent past.