  Recent maser surveys have shown that many potential OH/IR stars have no OH
masers in their circumstellar envelopes, despite the modest requirements which
should be implicitly met by IRAS colour-selected candidates. It has been
suggested that these OH/IR colour mimics must have a degenerate companion which
dissociates OH molecules and disrupts the masing action, ie. that they are
related to symbiotic Miras. Coincidentally, there is a paucity of long-period
symbiotic Miras and symbiotic OH/IR stars. Phenomonologically, those that are
known seem to cluster in the zone where field Miras transform into OH/IR stars.
If it could be proven that OH/IR colour mimics contain a degenerate star, that
observable evidence of this star is hidden from view by CS dust whilst it
slowly accretes from the wind of its Mira companion, then we have an excellent
explanation for not only the existence of OH/IR colour mimics, but also for the
low observed frequency of symbiotic OH/IR stars and the common occurrence of
very slow novae in long-period symbiotic Miras. Here, we employ radio continuum
radiation (which should escape unhindered from within the dust shells) as a
simple probe of the postulated hot degenerate companions which would inevitably
ionize a region of their surrounding gas. We compare the radio and infrared
properties of the colour mimics with those of normal symbiotic Miras, using the
strong correlation between radio and mid-IR emission in symbiotic stars. We
show that if a hot companion exists then, unlike their symbiotic counterparts,
they must produce radiation-bounded nebulae. Our observations provide no
support for the above scenario for the lack of observed masers, but neither do
they permit a rejection of this scenario.
