Time-resolved hadronic particle acceleration in the recurrent Nova RS Ophiuchi

TL;DR

This study reports the detection of very-high-energy gamma rays from the recurrent nova RS Ophiuchi, revealing insights into particle acceleration mechanisms in shock environments following nova outbursts.

Contribution

It provides the first time-resolved observations of VHE gamma rays from RS Ophiuchi, supporting a hadronic acceleration model in nova shocks.

Findings

VHE gamma rays detected up to a month after outburst

Temporal profile similar to GeV emission with a two-day delay

Supports hadronic particle acceleration in dense stellar winds

Abstract

Recurrent Novae are repeating thermonuclear explosions in the outer layers of white dwarfs, due to the accretion of fresh material from a binary companion. The shock generated by ejected material slamming into the companion star's wind, accelerates particles to very-high-energies. We report very-high-energy (VHE, $\gtrsim100$\,GeV) gamma rays from the recurrent nova RS\,Ophiuchi up to a month after its 2021 outburst, using the High Energy Stereoscopic System. The VHE emission has a similar temporal profile to lower-energy GeV emission, indicating a common origin, with a two-day delay in peak flux. These observations constrain models of time-dependent particle energization, favouring a hadronic emission scenario over the leptonic alternative. This confirms that shocks in dense winds provide favourable environments for efficient cosmic-ray acceleration to very-high-energies.