How about two neutron stars or two black holes merging?
Or, one planet or one star being sliced and diced by a black hole or neutron star?
I think you could get a pretty good light show from any of those possibilities, and not much radiation, because of the intense gravity.
There was a great thread on this subject years ago. It is unlikely that the Magi were following a single prominent feature in the sky like a comet or supernova. Scripture itself pretty much confirms this. When the Magi showed up in Jerusalem and told Herod they had “followed” a star to get there, Herod had to ask his scholars and advisors when the star appeared. If this “star” had been something as remarkable as a comet or supernova, he wouldn’t have needed to ask about it because it would have been clearly visible to everyone.