I did not read any of the replies yet so I may look like a donk here, but I think BB is testing Hero for a K by making the half pot bet. Without specific reads, he can have any two cards to make this play. He's heard Mike Van Sexton enough to know that you can "earn" pot by being aggessive.

Since you have position, I would either smooth call as if I had the K and wanted him to continue betting the turn, or possiblt make a reasonable reraise that doesn't commit too many chips. Maybe pop it to t200 and see what he does.

I might let it go on the turn if I'm unimproved and he gets aggressive.

John