Science is once again victim of catchy headlines.

From the New Scientist article which Yahoo Finance(!) is quoting:

What about those alien megastructures? Schafer is unconvinced. “The alien-megastructure idea runs wrong with my new observations,” he says, as he thinks even advanced aliens wouldn’t be able to build something capable of covering a fifth of a star in just a century. What’s more, such an object should radiate light absorbed from the star as heat, but the infrared signal from Tabby’s star appears normal, he says.

So tl;dr: We don't know what it is, but it's probably not aliens.