The Radio Counterparts to the Binary O4+O4 System CEN 1 in NGC 6618, the Cluster Ionizing M17

Abstract

We present the analysis of VLA archive observation made in the year 2000 at 8.46 GHz toward M17. In the region of the stellar cluster NGC 6618 we detect seven compact radio sources, of which four have Chandra X-ray counterparts. Two of the radio+X-ray sources coincide positionally with the two O4 stars that form the binary systen CEN 1. These stars are the main ionizing sources of the M17 H II region and the brightest X-ray objects in the zone. The observed 8.46 GHz ux densities exceed by an order of magnitude the values expected from free-free emission from a wind. An additional archive observation made in 1988 at 4.86 GHz suggests variability in the radio sources associated with CEN 1.