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

TL;DR

This paper reports the discovery of a bow-shock nebula around the CV star FY Vul, confirmed through deep imaging and spectroscopy, highlighting the interaction between the star's wind and the interstellar medium.

Contribution

First detection of a bow-shock nebula around a Z Camelopardalis-type CV using amateur telescope imaging and spectroscopic analysis.

Findings

Identification of a bow shock in [O III] emission in front of FY Vul

Detection of a recombination wake near the star

FY Vul is among six CVs with associated bow shocks and nebulae

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.