A black hole can torment a star for years, rather than rip it apart immediately. Tidal forces are when the hole's gravity stretches the star: the near side is pulled harder than the far side. Usually, getting too close rips the star apart instantly — that's a tidal disruption event. But if the star stays a bit farther out, the critical tear doesn't happen. Instead, like a rubber band that snaps after many gentle tugs, the star wears down bit by bit, losing mass in chunks. Each loss is a brilliant flare.
The flares can flicker unpredictably: not every pass strips material, so the signals come and go. That explains the odd behavior of the source J0456-20. A similar instability was described almost a century ago by Subrahmanyan Chandrasekhar for white dwarfs — stellar remnants that can't grow beyond a limit. Now the same principle links energy dissipation in the star with black hole flares.
If the Sun were in that star's place, each flare would shine brighter than our entire Galaxy — and it would last for centuries.
Like in 'Interstellar': Gargantua's tidal forces slowly wrecked planets in its orbit.