The Optical Spectrum of the Planetary Nebula NGC 2440

Abstract

Wavelengths and identifications have been provided for approximately 300 lines between 3660 and 10125 Å in the spectrum of the bipolar planetary nebula NGC 2440. These lines measured with the Hamilton echelle spectrograph at Lick Observatory and supplemented by published IUE results are used to construct diagnostic diagrams and derive ionic concentrations. The electron temperature indicated by [O iii] is ~14,200 K; the electron density is ~5000 cm^-1. With the aid of a standard model and an ionization correction factor method, we obtain a set of abundances that are compared with the Sun and with results of previous studies. As with other Peimbert Type I's, He and N are enriched as compared with the Sun; C is likewise overabundant. NGC 2440 evolved from a progenitor star that was more massive than the Sun. The central star temperature seems close to 180,000 K.