paper

What determines the -ray luminosities of classical novae?

arXiv:2508.15900 · doi:10.1093/mnras/staf2270

Abstract

Classical novae in the Milky Way have now been well-established as high-energy GeV -ray sources. In novae with main-sequence companions, this emission is believed to result from shocks internal to the nova ejecta, as a later fast wind collides with an earlier slow outflow. To test this model and constrain the -ray production mechanism, we present a systematic study of a sample of recent Galactic novae, comparing their -ray properties (-ray luminosity and duration) with their outflow velocities, peak -band magnitudes, and the decline times of their optical light curves (). We uniformly estimate distances in a luminosity-independent manner, using spectroscopic reddening estimates combined with three-dimensional Galactic dust maps. Across our sample, -ray luminosities (100 MeV) vary by three orders of magnitude, spanning erg s. Novae with larger velocity of the fast outflow (or larger differential between the fast and slow outflow) have larger -ray luminosities, but are detectable for a shorter duration. The optical and -ray fluxes are correlated, consistent with substantial thermal emission in the optical from shock-heated gas. Across six novae with -ray and infrared light curves, evidence for dust formation appears soon after the end of the detected -ray emission. Dusty and non-dusty novae appear to have similar -ray luminosities, though novae that have more material processed by the shocks may be more likely to form dust. We find that the properties of the -ray emission in novae depend heavily on the ejecta properties, and are consistent with expectations for internal shocks.

arXiv comment58 pages, 76 figures, Accepted by MNRAS

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