[oe] Deleting branches in main repository

[Ulf Samuelsson]

Still learning about git, and I managed to create one branch by mistake
  origin/local
There is also an obsolete branch which I want to remove 
  origin/ulf/atmel

Only want to keep the following.
  origin/ulf/linux

How can I clean up?

tried
git push origin :origin/local
and
git push origin :local
but this does not work

BR
Ulf Samuelsson