Multi-messenger events

You have heard that LIGO is a gravity wave detector, and has spotted signals consistent with black hole mergers. They've actually spotted a number of things, and with the Virgo detector running now, they're able to narrow down the window to tell where things come from.

A few days ago they spotted what looks like a neutron star merger. A neutron star has lots of ordinary matter to play with, so you expect a more brilliant explosion than with black holes--and there was a gamma ray signal within 2 seconds of that neutron star merger event. The merger proper is the last act of the event, and a lot of the fireworks come along with the initial splashing.

LIGO and Virgo and IceCube and FERMI and others send messages to each other when something interesting happens. Initially IceCube didn't get a good estimate, but on followup we found a neutrino track about 360 seconds before the merger. We issued our own bulletin.

6 minutes seems like a pretty long time, but even before the neutron stars touch they could be distorting each others' surfaces though tidal effects and blasting stuff around, or having dramatic magnetic field interactions (which could accelerate protons to wild speeds), or some other general relativistic interactions that I'm not thinking of yet. I don't have a good intuition for what those should look like.

That should generate lots of gamma rays too, but there could be so much stuff clouded around that a lot of the gamma rays might not get through. (Think of it like not seeing a fire because of the smoke.)

I suspect that more refined analysis will not make the time agreement closer, and that what will really help us decide what's going on is finding more events like it, and learning what the timing patterns are. So far the event rate seems high enough that we can be optimistic. But it will take a few years.