What does the "S" stand for in the S2398 star?

Question

What does the "S" stand for in the S2398 star?

Answer 1

I'm pretty sure it's the grid point it exists in space.

Answer 2

The S stands for "Struve", the German astronomer who meticulously studied and catalogued double stars.

Struve 2398 is a binary star system in the constellation Draco.  Both are red dwarfs, both are variable flare stars.

Their orbital period is about 408 years, at an average distance of about 56 AU, orbital eccentricity around 0.53.