Pulse of a dead star? Nope. What they are looking at is an embryonic galaxy. A galactic seed which will eventually eject from the Milky Way many years into the future and grow into a galaxy itself.
Besides, my readers already know what a dead star looks like. We have them in our neighborhood and they sure as hell don't emit powerful gamma rays. They are dead stars, meaning they are dead, a.k.a. NOT ACTIVE. Here is Mercury. Does anybody see huge gamma rays coming out of it? I sure don't. You know why? Its dead! Its the eventual fate of all stars when they die. They are destined to cool and shrink into giant rocks with iron/nickel cores. There's the General Unified Theory people have been looking for. Unfortunately it does not include general relativity or quantum mechanics. Oh well! Should it be a surprise that progress happens in unpredictable ways?