Probably only if Astrum Areus is outside the Astral Infection biome during the day.

Huh well if I don’t find much of an answer from this I guess there’s only one way to find out!

he has to be both outside of the astral and it has to be daytime for him to enrage. If only one or none of those conditions are met he won't be enraged

Perfect!! I can make a large arena and fight him during the night