The planetary nebula IC 4776 and its post-common-envelope binary central star

Abstract

We present a detailed analysis of IC 4776, a planetary nebula displaying a morphology believed to be typical of central star binarity. The nebula is shown to comprise a compact hourglass-shaped central region and a pair of precessing jet-like structures. Time-resolved spectroscopy of its central star reveals periodic radial velocity variability consistent with a binary system. While the data are insufficient to accurately determine the parameters of the binary, the most likely solutions indicate that the secondary is probably a low-mass main sequence star. An empirical analysis of the chemical abundances in IC 4776 indicates that the common-envelope phase may have cut short the AGB evolution of the progenitor. Abundances calculated from recombination lines are found to be discrepant by a factor of approximately two relative to those calculated using collisionally excited lines, suggesting a possible correlation between low abundance discrepancy factors and intermediate-period post-common-envelope central stars and/or Wolf-Rayet central stars. The detection of a radial velocity variability associated with binarity in the central star of IC 4776 may be indicative of a significant population of (intermediate-period) post-common-envelope binary central stars which would be undetected by classic photometric monitoring techniques.

Accepted for publication in MNRAS

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Cited by in corpus (5)

• C/O ratios in planetary nebulae with dual-dust chemistry from faint optical recombination lines
• Accounting for planet-shaped planetary nebulae
• IFU spectroscopy of Southern PNe: VII Photo-ionization modelling of intermediate excitation class objects
• The post-common-envelope binary nucleus of the planetary nebula IC~4776: Neither an anomalously long orbital period nor a Wolf-Rayet binary
• Variable jets at the termination of the common envelope evolution