  The recent discovery by LIGO/Virgo of a merging binary having a $\sim 23
M_\odot$ black hole and a $\sim 2.6 M_\odot$ compact companion has triggered a
debate regarding the nature of the secondary, which falls into the so-called
mass gap. Here we explore some consequences of the assumption that the
secondary was a neutron star (NS). We show with concrete examples of heretofore
viable equations of state (EOSs) that rapid uniform rotation may neither be
necessary for some EOSs nor sufficient for others to explain the presence of a
NS. Absolute upper limits for the maximum mass of a spherical NS derived from
GW170817 already suggest that this unknown compact companion might be a slowly
or even a nonrotating NS. However several soft NS EOSs favored by GW170817 with
maximum spherical masses $\lesssim 2.1 M_\odot$ cannot be invoked to explain
this object, even allowing for maximum uniform rotation. By contrast,
sufficiently stiff EOSs that yield $2.6 M_\odot$ NSs which are slowly rotating
or, in some cases, nonrotating, and are compatible with GW170817 and the
results of NICER, can account for the black hole companion.
