Extended Non-Thermal Emission Possibly Associated with Cyg OB2 #5

Abstract

Cyg OB2 #5 is a contact binary system (O6.5-7+O5.5-6) with associated radio continuum emission. Two compact (≤0.”3) radio continuum components have been reported previously: the primary one is associated with the contact binary and the secondary one is an arc-like source ∼0.”8 to the NE of the primary. This arc-like source results from the interaction of the winds of the contact binary and a B-type star in the region. In this paper we report the detection of an extended (∼30”), non-thermal component to the NE of the compact components. We propose that this extended emission could be an unresolved background source (i.e. a radio galaxy), extended galactic emission, or non-thermal emission related with relativistic electrons that are produced in the shock between the contact binary and the B-type star and that are carried away to large distances by the wind from the contact binary.