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

TL;DR

The paper reports the discovery of a faint bow-shock nebula, StDr 90, surrounding the Z Camelopardalis-type cataclysmic variable FY Vulpeculae. Using deep images from amateur observatories and spectroscopic follow-up with the HET/LRS2-B, the authors confirm the CV nature of FY Vul and reveal a prominent [O III] 5007 Å bow shock in front of the star, as well as a nearby faint Hα recombination wake. The findings add FY Vulpeculae to the small but growing class of CVs associated with bow shocks and off-center nebulae, supporting a common picture in which luminous accretion-disk winds drive shocks into the ambient ISM. The work underscores the value of citizen-science–level imaging, archival surveys like IPHAS, and targeted spectroscopy for diagnosing wind-ISM interactions in CVs, with broader implications for mass loss and feedback in binary systems.

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] 5007 A, 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 Halpha-emitting nebula, which we interpret as a "recombination wake," i.e., a Stromgren 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.