I wonder if 500 million years is long enough for an intelligent civilization to come up with some sort of early warning system such as figuring out which stars might be turning dangerous. The article doesn't say how long the bursts last.
The burst lasts as long as it takes the stuff (radiation) get past the planet. That is only a few seconds. That radiation is travelling at light speed so given our present knowledge an early warning system is unthinkable. However for a star big enough to go supernova, expected life expectancy and spectral analysis can give you some estimate rounded to the 10s or 100s of millions of years.
