Embeddings of Ree unitals in a projective plane over a field

Abstract

We show that the Ree unital R(q) has an embedding in a projective plane over a field F if and only if q=3 and F8 is a subfield of F. In this case, the embedding is unique up to projective linear transformations. Besides elementary calculations, our proof uses the classification of the maximal subgroups of the simple Ree groups.