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EGB 6 is a faint, large, ancient planetary nebula (PN). Its central star, ahot DAOZ white dwarf (WD), is a prototype of a rare class of PN nucleiassociated with dense, compact emission-line knots. The central star also showsexcess fluxes in both the near- (NIR) and mid-infrared (MIR). In a 2013 paper,we used Hubble Space Telescope (HST) images to show that the compact nebula isa point-like source, located 0".16 (~118 AU) from the WD. We attributed the NIRexcess to an M dwarf companion star, which appeared to coincide with the denseemission knot. We now present new ground-based NIR spectroscopy, showing thatthe companion is actually a much cooler source with a continuous spectrum,apparently a dust-enshrouded low-luminosity star. New HST images confirm commonproper motion of the emission knot and red source with the WD. The I-band, NIR,and MIR fluxes are variable, possibly on timescales as short as days. We canfit the spectral-energy distribution with four blackbodies (the WD, a ~1850 KNIR component, and MIR dust at 385 and 175 K). Alternatively, we show that theNIR/MIR SED is very similar to that of Class 0/I young stellar objects. Wesuggest a scenario in which the EGB 6 nucleus is descended from a wide binarysimilar to the Mira system, in which a portion of the wind from an AGB star wascaptured into an accretion disk around a companion star; a remnant of this diskhas survived to the present time, and is surrounded by gas photoionized by UVradiation from the WD.

The Nucleus of the Planetary Nebula EGB 6 as a Post-Mira Binary