Gamma-ray bursts [1] are a class of observations, not single event. Some of them may originate from relativistic jets [2] emitted by massive, spinning, charged objects colliding (e.g. black holes). Those jets' intensity is not uniform; if it's pointed at the Earth, that's worse than if it's pointed perpendicularly to it.

There are other mechanisms proposed that columnate the emission [3][4]. These involve a star's rotation creating a radiating column along the star's axis. (I'm not sure if the atoms in that column radiate with a bias.)

[1] https://en.wikipedia.org/wiki/Gamma-ray_burst

[2] https://en.wikipedia.org/wiki/Astrophysical_jet

[3] https://arxiv.org/abs/astro-ph/9808355

[4] https://www.plasma-universe.com/gamma-ray-bursts/