  Rapid rotation and nonradial pulsations enable Be stars to build decretion
disks, where the characteristic line emission forms. A major but unconstrained
fraction of Be stars owe their rapid rotation to mass and angular-momentum
transfer in a binary. The faint, stripped companions can be helium-burning
subdwarf OB-type stars (sdOBs), white dwarfs (WDs), or neutron stars. We
present optical/near-IR CHARA interferometry of 37 Be stars selected for
spectroscopic indications of low-mass companions. From multi-epoch $H$- and/or
$K$-band interferometry plus radial velocities and parallaxes collected
elsewhere, we constructed 3D orbits and derived flux ratios and absolute
dynamical masses of both components for six objects, quadrupling the number of
anchor points for evolutionary models. In addition, a new wider companion was
identified for the known Be + sdO binary 59 Cyg, while auxiliary VLTI/GRAVITY
spectrointerferometry confirmed circumstellar matter around the sdO companion
to HR 2142. On the other hand, we failed to detect any companion to the six Be
stars with $\gamma$ Cas-like X-ray emission, with sdOB and main-sequence
companions of the expected spectroscopic mass being ruled out for the
X-ray-prototypical stars $\gamma$ Cas and $\pi$ Aqr, leaving the elusive WD
companions as the most likely companions, as well as a likely explanation of
the X-rays. No low-mass main-sequence close companions were identified in the
other stars.
