The γ $\gamma$ -ray sources in classical novae

Abstract

The interaction between novae ejecta and accretion disks or circumbinary (CB) disks surrounding nova systems based on the diffusive shock acceleration (DSA) mechanism are investigated. Results suggest that interaction between the novae ejecta and CB disks most probably produce $\gamma$ -rays. Both leptonic and hadronic scenarios can feasibly produce $\gamma$ -rays in CB disks. A grid is calculated in order to discuss the $\gamma$ -ray sources in classical novae (CNe), and results indicated that the mass of a white dwarf and the orbit period in CNe can greatly affect the production of $\gamma$ -rays. According to the proposed grid and synthesis population method, it is estimated that the percentage of CNe that can produce $\gamma$ -rays ranges from approximately 0.17 % to 51 % for leptonic scenarios when the magnetic field strength in the shock region ranges from 0.005 G to 0.02 G. The occurrence rate of $\gamma$ -ray CNe ranges from approximately $1~\mbox{yr}^{-1} \mbox{ to } 27~\mbox{yr}^{-1}$ in the galaxy. The corresponding percentage ranges from approximately 64 % to 97 % in hadronic scenarios, while the occurrence rate of $\gamma$ -ray CNe ranges from approximately $35~\mbox{yr}^{-1} \mbox{ to } 52~\mbox{yr}^{-1}$ in the galaxy.