Fermi-LAT upper limits on gamma-ray emission from colliding wind binaries

Abstract

Context: Colliding wind binaries (CWBs) are thought to give rise to a plethora of physical processes including acceleration and interaction of relativistic particles. Observation of synchrotron radiation in the radio band confirms there is a relativistic electron population in CWBs. Accordingly, CWBs have been suspected sources of high-energy gamma-ray emission since the COS-B era. Theoretical models exist that characterize the underlying physical processes leading to particle acceleration and quantitatively predict the non-thermal energy emission observable at Earth. Aims: We strive to find evidence of gamma-ray emission from a sample of seven CWB systems: WR 11, WR 70, WR 125, WR 137, WR 140, WR 146, and WR 147. Theoretical modelling identified these systems as the most favourable candidates for emitting gamma-rays. We make a comparison with existing gamma-ray flux predictions and investigate possible constraints. Methods: We used 24 months of data from the Large Area Telescope (LAT) on-board the Fermi Gamma Ray Space Telescope to perform a dedicated likelihood analysis of CWBs in the LAT energy range. Results: We find no evidence of gamma-ray emission from any of the studied CWB systems and determine corresponding flux upper limits. For some CWBs the interplay of orbital and stellar parameters renders the Fermi-LAT data not sensitive enough to constrain the parameter space of the emission models. In the cases of WR140 and WR147, the Fermi-LAT upper limits appear to rule out some model predictions entirely and constrain theoretical models over a significant parameter space. A comparison of our findings to the CWB eta Car is made.

9 pages, 3 figures

References in corpus (7)

• Physical Properties of Wolf-Rayet Stars
• Radio, X-ray, and gamma-ray Emission Models of the Colliding Winds Binary WR 140
• Detection of Gamma-ray Emission from the Eta-Carinae Region
• γ^2 Velorum: Orbital Solution and Fundamental Parameter Determination with SUSI
• The modulation of the gamma-ray emission from the binary LS 5039
• Direct constraint on the distance of y2 Velorum from AMBER/VLTI observations
• Gamma-ray follow-up studies on Eta Carinae

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