This surprising result shows that, in the right circumstances, white dwarfs are capable of mimicking black holes, the most luminous objects we know of.

Black hole accretion disks produce energy at all frequencies. They didn't say if the above object was luminous in anything except xray. Based on their explanation theorizing that a shock wave was the source of the xrays then it should only have been mostly xrays rather than full spectrum.

The progenitor of the white dwarf must have been even more massive than its companion, to go through the main sequence. Shouldn't it become a neutron star? Or a supernova? What is roughly the most massive star that can produce a WD?

The Chandrasekhar limit is 1.44 solar masses. Above this level, a star's condensing mass can overcome electron degeneracy pressure and form a neutron star.

material was probably collecting on the surface of the white dwarf from the B star and eventually underwent runaway thermonuclear burning that was seen on Earth as a nova explosion

IMO the similar things may happen with more massive stars and black holes and after then an electroweak burning of neutrinos and/or axions may happen under temporal formation of bosenova. Recently we could even read a theory for it right here at PhysOrg, so you can see, it's not just a random idea of my peculiar mind. This essentially provides the mechanism for occasional gamma ray bursts, as observed around many black holes, including the central black hole of Milky Way. These bursts were conjectured before twenty years already with French astronomer LaViolette. I do consider these bursts as one of probable scenarios of global warming events.

Here are various indicia of neutrino atmosphere around Sun, which appears like thick ring, ejecting the neutrinos from solar core in thick jets. The neutrinos influent the speed of radioactive elements decay, which has been observed during flyby of few spaceprobes. It would indicate, that the dark matter is distributed around Sun in similar way, like around massive galactic clusters.

If we estimate the mean velocity of neutrinos, which are in thermodynamic equilibrium with CMBR radiation of 3K temperature), you'll get a velocity, which is quite close to the escape velocity of Sun (560 km/sec, or so). So it may be possible, that the solar neutrinos cumulate and condense around Sun like the sparse invisible atmosphere and they occasionally collapse into it under formation of solar flares. This event may be triggered, when the Sun appears in the gravitational shadow of multiple massive bodies, i.e. during eclipses and/or planetary conjunctions.

The ejection of neutrinos during solar flares may even influence the motion of plasma outside of Sun, as some observations indicate. I presume, the neutrinos ejected from Sun during flares accelerate the decay of radioactive elements inside of Earth crust and they cause heat waves there, which may result into quakes. In this way, the processes beneath the surfaces of both massive bodies are mutually connected through antimatter particles (negative curvature of space-time) in similar way, like the processes above their surfaces, where the space-time curvature is positive (climate changes induced with solar wind).

Apparently, there is still lotta physics to research...

"We think that this incredible X-ray flash was not due to accretion onto a black hole but was instead due to a nova explosion on a white dwarf that took place close to a hot massive star. This was something that we, as astronomers, have never seen before."

Yes, likely something similar happens on the galactic supermassive core stars, as LaViolette contends.

http://phys.org/n...559.html

BTW, Val, LaViolette is American. He once worked for the US PTO, as an examiner.