Villain is unkown. What's your play here, and what are your plans for the turn?
10NL
9 players

Stack sizes:
UTG: $9.50
UTG+1: $6.35
MP1: $10.45
MP2: $9.75
MP3: $9.60
Hero: $9.85
Button: $14.25
SB: $10.85
BB: $1.90

Pre-flop: (9 players) Hero is CO with
UTG calls, 4 folds, Hero raises to $0.5, Button calls, SB folds, BB calls, UTG calls.

Flop: ($2.05, 4 players)
BB checks, UTG checks, Hero bets $1.4, Button raises to $2.8, 2 folds, Hero ?