Discovery of a new classical nova shell around a nova-like cataclysmic variable

TL;DR

This study identifies a nebula as a classical nova shell surrounding a cataclysmic variable star, based on detailed imaging, spectroscopy, and variability analysis, revealing its true nature as a nova remnant.

Contribution

The paper presents the first evidence of a classical nova shell around a nova-like cataclysmic variable, combining imaging, spectral analysis, and variability data.

Findings

Nebula shows nitrogen-enriched knots and a bow-shock structure.

Central star exhibits a 4.26-hour binary period.

Optical spectrum resembles that of a nova-like CV.

Abstract

The morphology and optical spectrum of IPHASXJ210205+471015, a nebula classified as a possible planetary nebula, are however strikingly similar to those of ATCnc, a classical nova shell around a dwarf nova. To investigate its true nature, we have obtained high-resolution narrow-band [O III] and [N II] images and deep GTC OSIRIS optical spectra. The nebula shows an arc of [N II]-bright knots notably enriched in nitrogen, whilst an [O III]-bright bow-shock is progressing throughout the ISM. Diagnostic line ratios indicate that shocks are associated with the arc and bow-shock. The central star of this nebula has been identified by its photometric variability. Time-resolved photometric and spectroscopic data of this source reveal a period of 4.26 hours, which is attributed to a binary system. The optical spectrum is notably similar to that of RWSex, a cataclysmic variable star (CV) of the UXUMa nova-like (NL) type. Based on these results, we propose that IPHASX J210205+471015 is a classical nova shell observed around a CV-NL system in quiescence.