I agree that aces can sometimes be slow-played in heads-up, as they make an excellent trapping hand. Players are willing to put a lot more chips in with TP and a good kicker heads-up. However, I would probably not give a free turn card here. I would also be unlikely to raise all-in when he came to life on the turn, but that's going to depend on your read on the player. How has he been betting with top pair?