accent-circumflex in math on an arbitrary letter

[Dr. Ing. Roland Krause]

Hi experts,
can anyone please tell me whether it is possible to have something like:
   o
   E
that is a small cicle over any letter in math mode. I know about
accent-circumflex but that doesnt seem to work for all letters and especially
not in mathmode.
I'd  be satisfied if it involves ERT.

Thanks
Roland