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We present a detailed study of the barium star at the heart of the planetarynebula Abell 70. Time-series photometry obtained over a period of more than tenyears demonstrates that the barium-contaminated companion is a rapid rotatorwith temporal variability due to spots. The amplitude and phasing of thephotometric variability changes abruptly, however there is no evidence for achange in the rotation period (P = 2.06~d) over the course of the observations.The co-addition of 17 high-resolution spectra obtained with VLT-UVES allow usto measure the physical and chemical properties of the companion, confirming itto be a chromospherically-active, late G-type sub-giant with more than +1~dexof barium enhancement. We find no evidence of radial velocity variability inthe spectra, obtained over the course of approximately 130~d with a singleadditional point some 8 years later, with the radial velocities of all epochsapproximately $-$10 \kms{} from the previously measured systemic velocity ofthe nebula. This is perhaps indicative that the binary has a relatively longperiod (P $\gtrsim$ 2~yr) and high eccentricity ($e\gtrsim$ 0.3), and that allthe observations were taken around radial velocity minimum. However, unless thebinary orbital plane is not aligned with the waist of the nebula or thesystemic velocity of the binary is not equal to the literature value for thenebula, this would imply an unfeasibly large mass for the nebular progenitor.

A detailed study of the barium central star of the planetary nebula Abell 70