Villian is fairly aggressive. What's the best value raise here?

Noble Poker 0.25/0.50, hand converted by the iPoker Converter at Talking-Poker

saw flop | saw showdown

Button Button ($67.80)
SB ($35.65)
BB Hero ($117.06)
UTG ($33.50)
UTG+1 ($21.73)
CO ($68.25)

Preflop: Hero is in the BB with A A
1 fold, UTG+1 checks, 1 fold, Button raises to 2.50, 1 fold, Hero raises to 6, 1 fold, Button calls 3.50.

Flop (12.75) 6 A 9
Hero bets 7.00, Button raises to 19.00, Hero ???