I do not know whether the usage of outright is correct. Not having found this structure on Google search engine, I'm curious about it.
The author is outright wrong.
The sentence seems to be grammatically correct. The word "outright" is an adverb in the sentence that modifies the adjective "wrong"; it means "completely". However, the use of the word in this sense isn't common. Instead, we can say "The author is absolutely/altogether/completely wrong.
The word "outright" as an adverb is usually used in the sense of "at once or immediate or directly".