Searching for nova shells around cataclysmic variables

TL;DR

This study searched for nova shells around 101 cataclysmic variables using Halpha imaging, discovering one shell around V1315 Aql and evidence of past eruptions in V2275 Cyg, providing insights into nova recurrence and CV evolution.

Contribution

First systematic search for nova shells around a large sample of CVs, identifying new shells and evidence of historical eruptions, enhancing understanding of nova recurrence and CV phases.

Findings

Discovered a nova shell around V1315 Aql, indicating a recent eruption.

Found tentative shell evidence around V1363 Cyg, a dwarf nova.

Detected a light echo around V2275 Cyg, suggesting an earlier eruption.

Abstract

We present the results of a search for nova shells around 101 cataclysmic variables (CVs), using Halpha images taken with the 4.2-m William Herschel Telescope (WHT) and the 2.5-m Isaac Newton Telescope Photometric Halpha Survey of the Northern Galactic Plane (IPHAS). Both telescopes are located on La Palma. We concentrated our WHT search on nova-like variables, whilst our IPHAS search covered all CVs in the IPHAS footprint. We found one shell out of the 24 nova-like variables we examined. The newly discovered shell is around V1315 Aql and has a radius of approx.2.5 arcmin, indicative of a nova eruption approximately 120 years ago. This result is consistent with the idea that the high mass-transfer rate exhibited by nova-like variables is due to enhanced irradiation of the secondary by the hot white dwarf following a recent nova eruption. The implications of our observations for the lifetime of the nova-like variable phase are discussed. We also examined 4 asynchronous polars, but found no new shells around any of them, so we are unable to confirm that a recent nova eruption is the cause of the asynchronicity in the white dwarf spin. We find tentative evidence of a faint shell around the dwarf nova V1363 Cyg. In addition, we find evidence for a light echo around the nova V2275 Cyg, which erupted in 2001, indicative of an earlier nova eruption approx.300 years ago, making V2275 Cyg a possible recurrent nova.