After all these years I thought we just made up our own reasons why "such and such" happens in Trek. Is there any reason why the Hobus star couldn't have produced an unusual looking subspace shockwave, like Praxis did?
Except that in the comic and flashback, the star just keeps on going nova, getting magically bigger that it will actually consume the galaxy in massive perfectly spherical fireball.
So maybe we're looking at some sort of fiery looking FTL version of the "level 12
generated by the trilithium explosive in "Generations" then? To the outside eye it'd look like the star is just getting bigger and bigger.
Oddly enough, we know of at least one other event that caused subspace shockwaves from stars going supernova; in season three of "Voyager", a number of subspace shock waves were generated as byproducts of the supernovae caused by the Q Continuum during their civil war.