We would like to be able to perform a free text search using an author name and return all posts credited to that author, is this possible with Low Search?
The method Jamie mentioned will indeed work. You can also try and use Low Author, which saves the author screen name as a searchable read-only field. Add that field to your entries, and you'll be able to use keywords to search by author.
Edit: If you're using Low Search 4+, you can now also use the Members filter. Once installed, use the parameters
members:screen_name (exact matches) or
members:search:screen_name (partial matches) with the same result.
I don't know if anything has changed in more recent versions, but Low himself suggested using Solspace's Preparse addon for cases like this: