Zerun the Artifical Star

Zerun, originally a brown dwarf was initially destined to become a "failed" star. But its fate would change when a super advance space civilization came across this star and decided to kick start a fusion reaction transforming it from a brown dwarf into an actual star. Then a core reactor was placed in the center to harvest the energy required for an civilization spanning multiple stars

(the idea of this star is from an anime series titled Space Battleship Yamato)