The scientists took a lot of measurements over a long period, and carefully tried to remove as much noise as possible. After this, they think the remaining perturbation can be explained by a system of smallish planets. One of those planets looks like it could support life in a similar way to how Earth supports life.
There is a chance this perturbation is just noise, but the authors obviously think that the planetary system hypothesis is strong enough to ask the community for collaborating or contradictory data.
The title could have hedged its bets by adding 'might be' or similar terminology, but I honestly don't think that adds much to the conversation.
I was going to include the famous "title ending in '?'" rule of thumb, but missed the fact that the actual article and the title here differ. The actual title is of course "Another Earth Just 12 Light-Years Away?" which makes much more sense given the content.