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We present the discovery of a white dwarf companion at 3.6" from GJ3346, anearby ($\pi\sim$42 mas) K star observed with SPHERE@VLT as part of an opentime survey for faint companions to objects with significant proper motiondiscrepancies ($\Delta\mu$) between Gaia DR1 and Tycho-2. Syrius-like systemslike GJ3346AB, which include a main sequence star and a white dwarf, can bedifficult to detect because of the intrinsic faintness of the latter. Theyhave, however, been found to be common contaminants for direct imagingsearches. White dwarfs have in fact similar brightness to sub-stellarcompanions in the infrared, while being much brighter in the visible bands likethose used by Gaia. Combining our observations with Gaia DR2 and with severaladditional archival data sets, we were able to fully constrain the physicalproperties of GJ3346B, such as its effective temperature(11$\times$10$^3\pm$500 K) as well as the cooling age of the system (648$\pm$58Myrs). This allowed us to better understand the system history and to partiallyexplains the discrepancies previously noted in the age indicators for thisobjects. Although further investigation is still needed, it seems that GJ3346,which was previously classified as young, is in fact most likely to be olderthan 4 Gyrs. Finally, given that the mass (0.58$\pm$0.01$M_{\odot}$)} andseparation (85 au) of GJ3346B are compatible with the observed $\Delta\mu$,this discovery represents a further confirmation of the potential of this kindof dynamical signatures as selection methods for direct imaging surveystargeting faint, sub-stellar companions.

A new white dwarf companion to the $\Delta\mu$ star GJ 3346