Being an Astrophysicist must be fun. You get to make stuff up about something you've never seen ... kinda like my 4-year old does.
Direct conversion of mass to energy via quark force hypercompression. The quark force (between, for example, a quark-antiquark pair) is interesting in that, unlike most other forces in nature it gets stronger as the particles in the system move apart (it takes more and more energy to pull them apart the further apart that they get). After enough energy has been put into the system, the additional energy "snaps" the bond, creating an anti-quark for the quark and a quark for the anti-quark (or some similar particles depending on the quark system; essentially creating mass out of energy in a very inefficient process). This is why "naked" quarks don't exist in nature..
Like most things in nature, the reverse process can occur too. If, for example, you had two quark-antiquark pairs and a sufficient means to collapse them (such as the density in the core of a neutron star of sufficient mass), a reaction could occur that would result in the mass being "halved" and energy being released.
(Note that the quark-antiquark pair example is somewhat contrived, but similar and essentially equivalent reactions resulting in very efficient matter to energy conversion should be just as possible with a dense neutron baryon mass).
I'm surprised they figured out the existence of quark stars yet failed to jump to this conclusion.
Pretty sad.
