The Peculiar Emission-line Object Tololo 26

Tololo 26 was identified in 1976 as a planetary nebula (PN) with peculiar line ratios, in particular [O III] $\lambda $4363/H$\gamma $ estimated \textgreater 1. Hawley (1981) obtained a detailed spectrum, which showed no [O II] or [N II] and a $\lambda $4363/H$\gamma $ ratio of \textgreater 2.0, all unusual for PN and indicative of high electron density. Hawley suggested that Tol 26 could show spectral changes over time. In 2011 spectra were obtained confirming a change in [O III]/H$\beta $. Analysis of the original spectrum implied a small amount of high-density ionized gas, occupying a region smaller than the solar system. Estimates from the 2011 spectrum are consistent with a decrease in density and temperature. BVRI colors obtained in 2012, combined with GALEX and 2MASS observations, describe an SED that can be fitted with contributions from a 100,000K WD, a G2 V companion and dust components at 1350K and 200K. This makes Tol 26 the second object, along with EGB 6, proposed to be a PN with emission lines coming from a small amount of ionized gas associated with a cool companion to the white dwarf. We propose that an accretion disk is formed around the companion during the PN formation phase. Tol 26 and EGB 6 could be precursors to barium stars and certain PN central stars with rapidly rotating companions.