ESPRESSO observations of the debris-accreting white dwarf WD 0141−675

Abstract

WD 0141−675 was reported as the first astrometrically detected white dwarf planet host candidate as part of the third data release from Gaia, just to be later retracted via a news item on the Gaia website. We present time-resolved, high-resolution optical Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) spectroscopy of WD 0141−675. A radial velocity analysis of the Ca k absorption line reveals a tentative periodic signal of $15.6/pm 0.9$ d and an amplitude modulation of $0.19/pm 0.11$ km s−1. Phase folding the ESPRESSO spectroscopy on this signal exhibits weak variability in the morphology of Ca k close to the core of the line. A violet-to-red ratio analysis of the Ca k line shows a periodic signal of $16.7/pm 1.0$ d. The periods from both methods agree, within their uncertainties, with half the period of the astrometric planet candidate, however, both measurements are of low statistical significance. Nonetheless, our results imply possible solutions to the mass function within the planetary regime. When combined with existing infrared photometry, which rules out a brown dwarf companion, our results yield a lower limit on the orbital inclination of ${/sim} 7^/circ$. Our study demonstrates that ESPRESSO observations are well capable of detecting short-period (days to weeks) giant planets orbiting white dwarfs.