NGC 40 : IUE observations of the nucleus.

Abstract

UV spectra of the nucleus of NGC 40 allow a derivation of an E(B-V) foreground reddening of 0.50 and a distance to the object of 980 pc; accordingly, T(eff) of 90,000 K, log L/L(solar) of 4.4, R of 0.66 R(solar), and M of 1.1 M(solar) are obtained. It is suggested that the discrepancy between the temperature determined from the UV emission of the nucleus and the much lower value inferred from the ionization of the nebula is due to a 'carbon curtain' at the nebula's inner edge, which may be quantitatively studied on the basis of the high resolution IUE spectrum obtained. A column density of 10 to the 18th/sq cm is inferred from a curve-of-growth analysis of the C II resonance lines.