Stars sometimes promotes deposit bonuses such as these, usually for tickets around certain events they are promoting. The latest was the sharkcage promo.
The shark cage was a nice promotion played in all 12 of them cashing 4 times if you sign up at a site through an affiliate then you usually get some weekly or monthly free rolls for earning a certain amount of points but the only thing going on right now for deposit on Stars is the Social Media Free roll deposit and get ticket for an $8000 free roll taking place on March 30