I've noticed some stellar classifications might look like this:
I assume it means it's a binary (or triple, etc) star system, but cannot find any literature to back this up.
Resources I've looked at:
- The Spectra of Stars (and Brown Dwarfs)
- Stellar Classification
- Star Type
- Spectral Type
- Spectral Class
- Morgan-Keenan Luminosity Class
- The classification of stellar spectra
- The Classification of Stellar Spectra
- Studies of multiple stellar systems
(There are more, but this list is getting a bit ridiculous.)
What does the plus actually mean?
EDIT: doing further research, it would appear as though you get multiple types of plusses, too:
⁺ (superscript) - Increase in strength / magnitude?
+ (regular) - A sibling star?
Where it potentially gets a bit confusing is that downloadable star catalogs appear to present both as regular
+, meaning you'd need to read it contextually.