  We examine the possibility that the light companion in the highly asymmetric
binary compact object coalescence event GW190814 is a hypernuclear star. We use
density functional theory with functionals that have been tuned to the
properties of $\Lambda$ hypernuclei as well as astrophysical constraints placed
by the masses of the most massive millisecond pulsars, the mass-radius range
inferred from the NICER experiment, and the binary neutron star merger event
GW170817. We compute general-relativistic static and maximally rotating
Keplerian configurations of purely nucleonic and hypernuclear stars. We find
that while nucleonic stars are broadly consistent with a neutron star being
involved in GW190814, this would imply no new degrees of freedom in the dense
matter up to 6.5 times the nuclear saturation density. Allowing for
hyperonization of dense matter, we find that the maximal masses of hypernuclear
stars, even for maximal rapidly rotating configurations, are inconsistent with
a stellar nature interpretation of the light companion in GW190814, implying
that this event involved two black holes rather than a neutron star and a black
hole.
