Phase-Resolved Infrared Spectroscopy and Photometry of V1500 Cygni, and a Search for Similar Old Classical Novae

TL;DR

This study uses phase-resolved infrared observations of V1500 Cyg and other old novae to investigate magnetic properties and emission mechanisms, revealing potential magnetic systems and dust-related phenomena in these systems.

Contribution

It provides the first detailed infrared analysis of V1500 Cyg and surveys old novae for magnetic signatures and dust emission using 2MASS and WISE data.

Findings

V1500 Cyg's near-infrared flux is partly due to cyclotron emission.

Old novae V446 Her and QV Vul may host magnetic primaries.

Many old novae show infrared detections possibly due to ionized shells.

Abstract

We present phase-resolved near-infrared photometry and spectroscopy of the classical nova V1500 Cyg to explore whether cyclotron emission is present in this system. While the spectroscopy do not indicate the presence of discrete cyclotron harmonic emission, the light curves suggest that a sizable fraction of its near-infrared fluxes are due to this component. The light curves of V1500 Cyg appear to remain dominated by emission from the heated face of the secondary star in this system. We have used infrared spectroscopy and photometry to search for other potential magnetic systems amongst old classical novae. We have found that the infrared light curves of V1974 Cyg superficially resemble those of V1500 Cyg, suggesting a highly irradiated companion. The old novae V446 Her and QV Vul have light curves with large amplitude variations like those seen in polars, suggesting they might have magnetic primaries. We extract photometry for seventy nine old novae from the 2MASS Point Source Catalog and use those data to derive the mean, un-reddened infrared colors of quiescent novae. We also extract WISE data for these objects and find that forty five of them were detected. Surprisingly, a number of these systems were detected in the WISE 22 mum band. While two of those objects produced significant dust shells (V705 Cas and V445 Pup), the others did not. It appears that line emission from their ionized ejected shells is the most likely explanation for those detections.