Extraordinarily Hot X-Ray Emission from the O9 Emission-Line Star HD 119682

Abstract

We present new optical and X-ray observations to show that the X-ray source 1WGA J1346.5-6255 previously associated with the SNR G309.2-0.6 can be unequivocally identified with the emission-line star HD 119682 located in the foreground open cluster NGC 5281. Images from Chandra in the X-ray band as well as from Magellan in the narrow optical Hα band show a coincidence of the source positions within 0.5". The X-ray source appears extremely hot for an OB star identified as of O9.7e type. XMM-Newton spectra show plasma temperatures of 1 and >8 keV with an X-ray luminosity of (6.2+/-0.1)×10³² ergs s^-1. The optical and X-ray properties are very reminiscent of the prototype emission-line star γ Cas. We discuss the ramifications of this similarity with respect to very early type emission-line stars as a new class of hard X-ray sources.