None of this fits with theories of supermassive black holes. E0102-72, located in the Small Magellanic Cloud. A diffraction grating on the telescope was used to spread out incoming x rays into a spectrum which could be scanned for the presence of specific elements in the stellar debris. Canizares estimated that as much as 10 solar masses' worth of oxygen was present in the wreckage of the older star, enough to furnish thousands of solar systems like ours with the breathable element needed for much of life on Earth. The brightening can last as short as two days or as long as 1000.
Longer durations suggest either large or very slow lensing objects.
David Bennett of Notre Dame reported at the AAS meeting on two such long-duration events in which the mass of the lens was calculated to be roughly 6 solar masses, too heavy to be a neutron star and more likely to be a black hole. Bennett speculates that the lone-wolf black holes form from supernova collapse and might be as common as neutron stars in the galaxy.