Gamma-ray sources like V407 Cygni in Symbiotic Stars

TL;DR

This paper models gamma-ray emission in symbiotic stars, suggesting that novae in certain systems can be significant gamma-ray sources, with maximum proton energies around 10^{11} eV and an occurrence rate of 0.5 to 5 per year.

Contribution

It introduces a simple acceleration model for gamma-ray production in symbiotic stars and identifies key system characteristics influencing gamma-ray emission.

Findings

Gamma-ray sources like V407 Cygni are potentially important in the Galaxy.

Maximum proton energies are around 10^{11} eV, rarely reaching 10^{15} eV.

Novae in D-type systems with ONe WDs are promising gamma-ray sources.

Abstract

Using a simple accelerating model and an assumption that $\gamma$-rays originate from $p-p$ collisions for a $\pi^0$ model, we investigate $\gamma$-ray sources like V407 Cygni in symbiotic stars. The upper limit of their occurrence rate in the Galaxy is between 0.5 and 5 yr$^{-1}$, indicating that they may be an important source of the high-energy $\gamma$-rays. The maximum energies of the accelerated protons mainly distribute around $10^{11}$ eV, and barely reach $10^{15}$ eV. The novae occurring in D-type SSs with ONe WDs and long orbital periods are good candidates for $\gamma$-ray sources. Due to a short orbital period which results in a short acceleration duration, the nova occurring in symbiotic star RS Oph can not produce the $\gamma$-ray emission like that in V407 Cygni.