against a 17/15 3bets 6 percent. Just sat down a little while ago and he's been pretty active. I was active on this table too like 24/20 or something. His bet sizing really bothers me. as well as my range on the turn....

Full Tilt Poker $0.50/$1 No Limit Hold'em - 4 players
The Official 2+2 Hand Converter Powered By DeucesCracked.com

BB: $101.50
CO: $320.80
BTN: $60.00
Hero (SB): $190.20

Pre Flop: Hero is SB with J A
2 folds, Hero raises to $3, BB raises to $9, Hero calls $6

Flop: ($18.00) 7 9 A (2 players)
Hero checks, BB bets $15, Hero calls $15

Turn: ($48.00) 4 (2 players)
Hero checks, BB bets $39, Hero folds

Fold is fine ... sucks tho

Unless you think he'd 3bet 99 you're usually only worried about AQ/AK here. He'll probably cbet the flop with his entire range.
Any read on the betsizing, have you seen the x9 bet before, is it strength or weakness?
I'd say he checks back his TT-KK and random 9xs so it's pretty much [bluffs;AK,AQ]. Guess it comes down to how often you think he bluffs given that you have one A and one A flopped it's 16 combos total so if you think he has 4 SCs or one offsuit hand like KQo in his bluffing range (and bluffs them often) there you can go with it.
He may actually check back AQ sometimes so I dunno. Generally I'd say I muck it unless I know he's capable of bluffing enough.
He pretty much has to follow through on the turn with all bluffs but he'd also size them smaller imo. and just because he has to follow through doesn't actually mean he will. In fact I'd say more people play it "one and done"