Cosmic ray bubbles from nova super-remnants and their contribution to local cosmic ray spectra

¹ Instituto de Astrofísica de Andalucía, CSIC, Granada 18008, Spain
² Max-Planck-Institut für Physik, 80805 München, Germany
³ Deutsches Elektronen-Synchrotron DESY, Platanenallee 6, 15738 Zeuthen, Germany

^★ Corresponding author; rlopezcoto@iaa.es

Received: 13 August 2024
Accepted: 8 March 2025

Abstract

Context. Several new phenomena have arisen in the area of study of the repeating thermonuclear explosions called novae. For example, recurrent novae have been proven to be efficient cosmic ray hadronic accelerators thanks to the recent observations of RS Ophiuchi by different γ-ray instruments. Novae have also been demonstrated to have the ability to carve large cavities into the interstellar medium (ISM), with parallels with the remnants of supernovae.

Aims. Our aims are to calculate the effects of novae on their surrounding media, and the distances over which these effects dominate over the average quantities that are measured in the ISM.

Methods. We calculated the filling factor of novae and their contribution to cosmic ray fluxes using cosmic ray propagation codes. To limit the atomic density of the ISM surrounding the region of RS Oph, we used Fermi-LAT observations of the region.

Results. The filling factor of novae in the Galaxy is not significant under all assumptions done in the paper. They do not dominate over the local cosmic ray fluxes, even at the lowest energies, for distances larger than a few parsecs. The particle density of the ISM surrounding them is, however, very much modified, being lowered by more than one order of magnitude with respect to galactic averages, confirming estimates done using other observatories.

Conclusions. Even though at global galactic distances, novae do not seem to be dominating cosmic ray transport, they have the power to modify the conditions of their surrounding ISM over parsec distances.