A Dual-Mask Coronagraph for Observing Faint Companions to Binary Stars

Observations of binary stars for faint companions with conventional coronagraphic methods are challenging, as both targets will be bright enough to obscure any nearby faint companions if their scattered light is not suppressed. We propose coronagraphic examination of binary stars using an apodized-pupil Lyot coronagraph and a pair of actively controlled image-plane masks to suppress both stars simultaneously. The performance is compared with imaging with a band-limited mask, a dual-mask Lyot coronagraph, and no coronagraph at all. An imaging procedure and control system for the masks are also described.