QU Carinae: a SNeIa progenitor?

TL;DR

This study analyzes optical spectra of QU Carinae, a cataclysmic variable, to evaluate its potential as a Type Ia supernova progenitor, highlighting wind signatures, nebular lines, and its relation to V Sge stars.

Contribution

It provides new spectral analysis of QU Car, supporting its classification as a possible SNeIa progenitor and linking it to V Sge stars and supersoft X-ray sources.

Findings

Detection of wind signatures and nebular lines in spectra.

Spectral evidence suggests carbon enrichment in the donor star.

Light curve shows low states similar to V Sge stars.

Abstract

Optical spectra obtained in 2006-07 of the nova-like cataclysmic variable QU Car are studied for radial velocities, line profiles, and line identifications. We are not able to confirm the reported 10.9 hr orbital period from 1982,partly because our sampling is not ideal for this purpose and also, we suspect, because our radial velocities are distorted by line profile changes due to an erratic wind. P-Cygni profiles are found in several of the emission lines, including those of C IV. Carbon lines are abundant in the spectra, suggesting a carbon enrichment in the doner star. The presence of [O III] 5007\AA and [N II] 6584\AA is likely due to a diffuse nebula in the vicinity of the system. The wind signatures in the spectra and the presence of nebular lines are in agreement with the accretion wind evolution scenario that has been suggested to lead to SNeIa. We argue that QU Car is a member of the V Sge subclass of CVs, and a possible SNeIa progenitor. It is shown that the recent light curve of QU Car has ~1 mag low states, similar to the light curve of V Sge, strengthening the connection of QU Car with V Sge stars, supersoft x-ray sources, and SNeIa progenitors.