Classical Novae at Radio Wavelengths

TL;DR

This study compiles and analyzes radio observations of 36 classical novae over five decades, revealing diverse emission mechanisms, including thermal and synchrotron, and identifying new classes and behaviors in their radio light curves.

Contribution

It provides a comprehensive dataset and analysis of radio emissions from classical novae, highlighting the presence of non-thermal synchrotron emission and introducing a class of novae with mildly evolved companions.

Findings

Radio emission is a mix of thermal and synchrotron processes.

Synchrotron emission observed in at least 25% of novae.

Identification of a class of novae bridging classical and symbiotic types.

Abstract

We present radio observations (1--40 GHz) for 36 classical novae, representing data from over five decades compiled from the literature, telescope archives, and our own programs. Our targets display a striking diversity in their optical parameters (e.g., spanning optical fading timescales, t_2 = 1--263 days), and we find a similar diversity in the radio light curves. Using a brightness temperature analysis, we find that radio emission from novae is a mixture of thermal and synchrotron emission, with non-thermal emission observed at earlier times. We identify high brightness temperature emission (T_B > 5x10^4 K) as an indication of synchrotron emission in at least 9 (25%) of the novae. We find a class of synchrotron-dominated novae with mildly evolved companions, exemplified by V5589 Sgr and V392 Per, that appear to be a bridge between classical novae with dwarf companions and symbiotic binaries with giant companions. Four of the novae in our sample have two distinct radio maxima (the first dominated by synchrotron and the later by thermal emission), and in four cases the early synchrotron peak is temporally coincident with a dramatic dip in the optical light curve, hinting at a common site for particle acceleration and dust formation. We publish the light curves as tables and encourage use of these data by the broader community in multi-wavelength studies and modeling efforts.