“Great book to read: Neutron Star by Dr. Forward.”

Wonderful book, but it was called Dragon’s Egg . I also
recommend RocheWorld . Both are excellent books about the
physics of unusual worlds, disguised as novels.

Like I said, both ideas are pretty cool.

Sure are! Metaphorically cool anyhow, the temps may be slightly on the hot side to put it mildly!

So take your pick: giant ice cubes slamming repeatedly at near light-speed into an ultra-compact neutron star and releasing petaton yields of energy somewhere in our galaxy, or a 5.5 billion light-year-distant black widow neutron star consuming its companion star and instigating a supernova event that utterly destroyed both, leaving nothing but rapidly expanding vapor with a tiny black hole at its heart.

Either way, the energies and temperatures and extremes involved are just staggering. 8)

I take it there will be astronomers working on choosing which of these ideas is correct based on other factors and digging through the specific data?

Of course if a similar GRB happens again at the exact same co-ordinates then it’d be very good evidence indeed for the devoured comet theory – now if only we could schedule a second comet to hit say a few months later …

(If only we had FTL craft and could go – very carefully – and see for ourselves. Sigh.)

Emission from very near the neutron star would be so affected, but could be accounted for. Emission from farther out (like from the resulting accretion disk the modelers suggest) would be substantially less gravity red-shifted, but that lack of any spectrum at all right there is hard to account for if the source really was within the few tens of thousands of light-years in our galaxy.

I’m pretty sure that neutron stars have a thin crust of normal matter above the “mantle” of degenerate matter, and that it should demonstrate absorption and emission lines just like any other object. I think the problem is that neutron stars are relatively tiny and quite dim. I’m not sure, but I think that the ferocious surface gravity would also tend to affect redshift measurements.

Gary 7

Both of the hypothesis offered to explain this could account for it, but to my mind if I had to choose between them, there are considerations that persuade me that the more distant binary model is more likely: first, although the collision of a Ceres-sized body with an otherwise isolated neutron star is possible and might account for it, such an event would be quite rare. This coupled with its location in Andromeda, a direction within our galaxy which is not particularly dense in terms of stellar population compared to directions closer to the midline of the galaxy’s plane and especially the central region where one would expect a much higher population of such neutron stars that could in principle do this (Andromeda is looking some 120 degrees away from the galactic center – toward the Milky Way’s OUTSKIRTS) defeats my enthusiasm for this scenario. Further, they’ve reported what seems to be a very distant galaxy detected at the proper location.

I have to favor the extragalactic model, but I would expect more variations of that scenario to emerge as other examples (ultra-long duration + thermal emission) show up. In a general way it already belongs to the basic in-spiraling theme of other (short-duration) GRB theories invoking in-spiraling binary neutron stars and/or stellar-mass black holes. GRB 101225A might represent a new intriguing sub-category in which one of the binary members hasn’t fully moved off the Main Sequence yet.

BTW @50 Lightndattic, etc: it’s been fairly well established in computer simulations that a supernova within a close binary doesn’t necessarily destroy the companion star.