I think this is a good place to have a look : https://en.wikipedia.org/wiki/Gravitational_time_dilation https://en.wikipedia.org/wiki/Gravitational_time_dilatio

I think this is a good place to have a look : https://en.wikipedia.org/wiki/Gravitational_time_dilation https://en.wikipedia.org/wiki/Gravitational_time_dilation My assumption is that the place that this burst is coming from is near a very large, very dense mass.