A note on the bundle underlying opers

In this note we write down a proof of the following well-known fact, in order to make the literature more transparent. Let 𝔤 be a simple Lie algebra, then for any smooth curve C , the bundle underlying any 𝔤 -oper depends only on the curve and it is induced by the canonical Aut O bundle Aut C on C . We also review the difference between 𝔤 -opers and opers for a general reductive group.