Reports about the Rangers and Hanson talking have been swirling the past few days, so this isn't a surprise. The Rangers have been looking for options to increase their starting pitching depth, and Hanson will join Colby Lewis, Nick Tepesch, and others in battling for the fifth starter spot (or, potentially, the fourth starter spot, if the Rangers decide to put Alexi Ogando back in the bullpen).
Hanson is a one-time stud prospect from the Atlanta system whose career has been derailed by injuries -- in particular, a rotator cuff injury that sapped him of his stuff. Atlanta traded him to the Angels for Jordan Walden prior to the 2013 season, and Hanson disappointed, putting up a 5.42 ERA in 73 innings, resulting in Anaheim non-tendering him.
Hanson, like so many of the Rangers' off-season additions, is a Scott Boras client, and he's also under team control for 2015, so if the Rangers like the progress he makes this season, they control his rights for another year, much like Neal Cotts last year.