FWIS3

As in, heavy enough that it should collapse into a black hole, but it hasn't:

https://www.theguardian.com/science/202 ... stronomers

In this case, Mundell said, something appears to have prevented the neutron star “noticing how massive it is”. One possibility is that the star was spinning so fast and with such immense magnetic fields that its collapse was delayed – something like how water stays inside a tilted bucket if it is swung around fast enough.

“This is the first direct glimpse that we may have of a hypermassive spinning neutron star in nature,” said Mundell. “My hunch is we’ll be finding more of them.”

So, likely a "mundane" explanation. Though I'm now remembering stuff I've heard about hypothetical quark stars... Rommie?

Wow I'd like to read up on this.
(Like I'd understand any of it... )

Yeah, so I'm not 100% sure how they got to their result because I'm not a GRB person. However, it is very important to note that this result is inferred from the data, over directly measured. What I mean is they saw this GRB and modeled a bunch of components from different kinds of emission (thermal, radiative, etc etc), and concluded to the best of their abilities it looks like there is an excess in mass that would explain it. This is not the same as, say, finding a pulsar and discovering based on the pulses the neutron's star mass must be above the threshold for it, which would be a direct measurement.

As such, while I think the result is interesting, I don't think everyone's gonna start saying it's a quark star. Instead it's much more likely that we don't truly understand everything behind GRB physics (which is easy to say bc we sure as hell don't), and are missing some component in the modeling.

Whatever it is, it is darn cool.