Analysis of nebulosity in the planetary nebula NGC 40

• Published in: Monthly notices of the Royal Astronomical Society 1983-11, Vol.205 (2), p.417-434
• Main Authors: Clegg, R. E. S., Seaton, M. J., Peimbert, M., Torres-Peimbert, S.
• Format: Article
• Language: English
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; Interstellar medium (ism) and nebulae in milky way; Planetary nebulae; Stellar systems. Galactic and extragalactic objects and systems. The universe
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/205.2.417

Optical and IUE spectra of a bright region of nebulosity in the planetary nebula NGC 40 have been combined for an analysis of the physical conditions and abundances in the nebula. Resulting abundances – log A(C) = 9.0, log A(O) = 8.9 and log A(N) = 8.4 – are typical of planetary nebulae and indicate that the nebulosity does not share the extreme abundances of the Wolf–Rayet WC8 central star. The continuum observed in the IUE spectra at an offset position can be fitted well to a calculated nebular continuum; the nebular lines are measured relative to the continuum and hence put on the same scale as optical lines measured relative to Hβ. The absence of stellar features in the offset spectra show that the optical depth for scattering by dust is less than 0.06. The emission in C IV λ 1549 from the nebula is anomalously strong. It may be explained, in part, as due to resonance scattering of radiation from the star or from the inner part of the nebula. New recombination lines of C II are identified in IUE spectra; their intensities relative to C II λλ 4267, 7230 in NGC 40 and IC 418 are analysed.