On $\epsilon$-mechanism driven pulsations in VV 47

TL;DR

This study re-examines the pulsations of VV 47, finding no evidence of variability or $$-mechanism driven pulsations, challenging previous claims and highlighting the difficulty of detecting such pulsations.

Contribution

The paper provides a rigorous re-analysis that refutes earlier claims of pulsations in VV 47, emphasizing the importance of conservative detection criteria in pulsation studies.

Findings

VV 47 showed no variability up to 0.52 mmag.

Previous oscillation detections were due to over-optimistic criteria.

Detection of $$-driven pulsations remains challenging.

Abstract

We report new observations of the central star of the planetary nebula VV 47 carried out to verify earlier assertions that the short-period pulsation modes detected in the star are driven by the $\epsilon$ mechanism. In our data, VV 47 was not variable up to a limit of 0.52 mmag in the Fourier amplitude spectrum up to the Nyquist frequency of 21.7 mHz. Given this null result we re-analyzed the data set in which oscillations were claimed. After careful data reduction, photometry, extinction correction, and analysis with a conservative criterion of S/N $\geq$ 4 in the Fourier amplitude spectrum, we found that the star was not variable during the original observations. The oscillations reported earlier were due to an over-optimistic detection criterion. We conclude that VV 47 did not pulsate during any measurements at hand; the observational detection of $\epsilon$-driven pulsations remains arduous.