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

• Main Author: Benaglia, Paula
• Format: Journal Article
• Language: English
• Published: 28-03-2016
• Subjects: Physics - High Energy Astrophysical Phenomena; Physics - Solar and Stellar Astrophysics
• DOI: 10.48550/arxiv.1603.07921

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.