An upper limit on the EUV flux from HD192273

Abstract

Cash et al.¹ reported the possible detection off an extreme ultraviolet (EUV) source in the constellation Pavo. They suggested HD192273 as a possible candidate and cited a TD-1 satellite observation indicating that this star is also unexpectedly bright at 1,565 Å. Wegner² reported visual photometric and spectroscopic data for HD192273 and concluded that it is apparently a normal B-type star. Shipman and Wegner³ have reviewed the available data on HD192273 and suggested that all of the observations could be explained if this object were an analogue of HZ22, an evolved, mass-exchange, binary. We report here a recent observation with the UV spectrometer (UVS) aboard the Voyager 1 spacecraft. An upper limit (2σ) of 8 × 10⁻³ photon cm⁻² s⁻¹ Å⁻¹ is placed on the 534–776 Å flux from HD192273 at the time of observation. This is ∼10% of the 500–780 Å flux reported from Pavo by Cash et al. The 1,565 Å flux observed by TD-1 is confirmed and is consistent with the stellar parameters determined by Wegner. Discounting the possibility that HD192273 is an EUV variable, it is probably not the potential source reported by Cash et al.