A Bow-Shock Nebula Around the Z Camelopardalis-type Cataclysmic Variable FY Vulpeculae ^∗

Abstract We present deep images of the faint nebulosity StDr 90, which we have discovered surrounds the cataclysmic variable (CV) star FY Vulpeculae. Archival photometric and spectroscopic observations, and a new optical spectrum, confirm that FY Vul belongs to the Z Camelopardalis subclass of CVs. Our imagery, obtained by accumulating long exposures with amateur telescopes equipped with CMOS cameras, shows a prominent bow shock in the light of [O iii ] λ 5007, collisionally excited in front of the star as it passes through a relatively dense region in the surrounding interstellar medium (ISM). FY Vul also lies near the edge of an extended faint H α -emitting nebula, which we interpret as a “recombination wake,” i.e., a Strömgren zone recombining after being photoionized by the star’s ultraviolet radiation. FY Vul joins five other CVs known to be associated with optical bow shocks and off-center nebulae. All of them are characterized by luminous accretion disks, which drive fast winds into the ISM that produce the bow shocks.