Is there a “dead star” companion to our sun, and if so, what kind of astral body is it in terms of scientific classification?

The sun does have a solar twin that is now a brown dwarf. It has not yet been discovered and this is because the information has been kept from the scientific community. So this is one of the many secrets held back that would advance science in undesirable directions from the extraterrestrial perspective. The same is true for the so-called planet X. The powers that be want no official recognition of anything to do with the Anunnaki, or their origins, or a more detailed exploration of local solar system bodies. There is always very careful editing of information acquired from the scientific explorations. Keep in mind that those done by the conventional scientific establishment coordinated through NASA and the University systems are essentially human-based, although with their minders, and the overlay of watchdogs to ensure they do not upset conventional wisdom. So they are innocent other than being corrupted by mind control to misdirect them and keep them focused on safe topics.