Hunting for Gas Giant Exoplanets Around White Dwarf GD 50

An Extreme-AO Search for Giant Planets around a White Dwarf --VLT/SPHERE performance on a faint target GD 50

Authors:

Xu et al

Abstract:

CONTEXT.

Little is known about the planetary systems around single white dwarfs although there is strong evidence that they do exist.

AIMS.

We performed a pilot study with the extreme-AO system on the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) on the Very Large Telescopes (VLT) to look for giant planets around a young white dwarf, GD 50.

METHODS.

We were awarded science verification time on the new ESO instrument SPHERE. Observations were made with the InfraRed Dual-band Imager and Spectrograph in classical imaging mode in H band.

RESULTS.

Despite the faintness of the target (14.2 mag in R band), the AO loop was closed and a strehl of 37\% was reached in H band. No objects were detected around GD 50. We achieved a 5-sigma contrast of 6.2, 8.0 and 8.25 mags at 0{\farcs}2, 0{\farcs}4 and 0{\farcs}6 and beyond, respectively. We exclude any substellar objects more massive than 4.0 MJ at 6.2 AU, 2.9 MJ at 12.4 AU and 2.8 MJ at 18.6 AU and beyond. This is the most stringent upper limit on a substellar object around any single white dwarf. We further show that SPHERE is the most promising instrument available to search for substellar objects around nearby white dwarfs.