Yeah, that's one thing I want to find out with the flat call. Not sure exactly how I'm going to respond to various scenarios here, though....
Anyhow, that mini-bet looks very weird to me. I think it's probably a weaker A (or, who knows... maybe even flush draw), but no telling. I don't think UTG has AA, as he would surely just flat call with that hand. But I do think he has at minimum AK in light of his raise.
I doubt I can lay this down, but I'd at least prefer to have them do the betting... and there might even be scenarios where I could lay it down. While AJ is unlikely, that hand has you drawing dead...
My flat call is pretty much a "wait and see" call to enable me to better put them on a hand.
Also, if you flat call and short-stack pushes, UTG is certainly going to know that he's up against a lot of strength here. I think this is a tough hand to play, though, and I'm really not at all sure how I'd proceed after that.