AJs 3-bet pot line check against unknown

[Mike MacIntosh]

Villain just sat down couple of hands ago.

PokerStars No-Limit Hold'em, $1.00 BB (6 handed) Poker Stars Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

saw flop|<font color="#C00000">saw showdown</font>

SB ($109.10)
<font color="#C00000">Hero ($110.05)</font>
UTG ($100.50)
MP ($95.50)
<font color="#C00000">CO ($108)</font>
Button ($65.55)

Preflop: Hero is BB with A[img]/images/graemlins/club.gif[/img], J[img]/images/graemlins/club.gif[/img].
<font color="#666666">2 folds</font>, <font color="#CC3333">CO raises to $4</font>, <font color="#666666">2 folds</font>, <font color="#CC3333">Hero raises to $13</font>, CO calls $9.

Flop: ($26.50) 5[img]/images/graemlins/diamond.gif[/img], T[img]/images/graemlins/heart.gif[/img], 5[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $17</font>, CO calls $17.

Turn: ($60.50) J[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, CO checks.

River: ($60.50) 2[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">CO bets $40</font>, Hero calls $40.

Standard?