Ultraviolet detection of the nucleus of NGC2440

Abstract

In a recent letter, Atherton et al.¹ announced the detection of the central, exciting star of the planetary nebula, NGC2440, on a narrow-band charge-coupled device (CCD) image obtained under excellent seeing conditions (1 arc s). They found it to be one of the hottest stars known. Here, we report the detection of the same star in ultraviolet spectra taken with the International Ultraviolet Explorer (IUE) satellite². The stellar parameters derived from these spectra, T ~200,000 K, L = 1,500 L_Ċ, log g = 7, M = 0.6 M_Ċ, are in accord with stellar evolutionary theory.