How do they know the radius?
If it's 5 times as massive and 1.5 times as big then it is 5/(1.5)^2 times the gravity at the surface. That comes out to 2.222...G's. What I'd like to know is how do they know the radius? The mass can be estimated by Newton's Laws, since they can see the Doppler shift in the star's spectrum caused by the wobble, but that doesn't tell them the density, this could be a compact rocky body or a gas giant. I've obviously missed something.