Is the stellar system WR 11 a gamma-ray source?

TL;DR

This study investigates whether the colliding-wind binary WR 11 is responsible for observed gamma-ray excess, analyzing radio data and source characteristics to support or refute its role as a gamma-ray emitter.

Contribution

The paper provides a detailed radio analysis of WR 11 and surrounding sources to evaluate its potential as a gamma-ray source, offering new insights into high-energy emissions from stellar systems.

Findings

WR 11 was not conclusively identified as the gamma-ray source.

A new radio source S6 may be a candidate for gamma-ray emission.

Most detected sources showed negative spectral indices, indicating non-thermal emission.

Abstract

Many early-type stars are in systems; some of them have been indicated as putative high-energy emitters. The radiation is expected to be produced at the region where two stellar winds collide. Compelling evidence of such emission was found only for the colliding-wind binary (CWB) Eta Car, which was associated to a GeV source. Very recently, the closest CWB, WR 11, was proposed as a counterpart of a 6sigma emission excess, measured with the Fermi LAT satellite. We looked for evidence to support or reject the hypothesis that WR 11 is responsible of the gamma-ray excess. Archive radio interferometric data at 1.4 and 2.5 GHz taken with the Australia Telescope Compact Array along sixteen different dates were reduced. The sizes of the field-of-view at 2.5 GHz and of the central region of the Fermi LAT excess are alike. We analyzed the emission of the field of WR 11, characterized the radio sources detected and derived their spectral indices, to investigate their nature. Eight sources with fluxes above 10 mJy were detected at both frequencies. All but one (WR 11) showed negative spectral indices. Four of them were identified with known objects, including WR 11. A fifth source, labeled here S6, could be a promising candidate to produce gamma-ray emission, besides the CWB WR 11.