Are fields that are hidden in a content type searchable?

Brass Contributor
I have five fields in one content type. Those are set by a service I programmed and I need them only for the search. The user should not even notice that those fields exist. The visibility of those fields is set to "optional" on a site level. But if they get inherited by my library, I set them all to "hidden" on a library level, because then they do not appear in the forms. If I now find crawled properties for my columns- will they be searchable even though they are not visible? How does the search behave in such a situation? I googled already and found some contradictive information here, so I hope some search experts here have the answer. Any help is highly appreachiated.
1 Reply
Funny that after four years there is no clear answer to this.