The quantities measured
The flare that the Zwicky Transient Facility caught in November 2025 was catalogued as TDE 2025abcr. Swift's ultraviolet and optical telescope measured it at about 30,000 degrees Celsius; for months the event outshone its host galaxy in the ultraviolet, reaching some ten billion times the Sun's luminosity. The source is a black hole of roughly a million solar masses, standing more than 30,000 light-years from the nucleus of a galaxy about 750 million light-years away towards Cetus.[1]
The numbers in the peer-reviewed paper are tighter: a peak blackbody temperature of 30,220 plus or minus 2,120 kelvin, a peak bolometric luminosity of 4.71 times 10 to the 43 ergs a second, a disrupting black hole of 10 to the 6.09 plus or minus 0.53 solar masses against the host's central black hole at 10 to the 8.82 plus or minus 0.65. The angular separation is 9.5 arcseconds, 9.3 kiloparsecs in projection. The mass carries half an order of magnitude of uncertainty, and that is the most honest figure we have when arguing about which black hole is which.[1]
How it was found
The search used an off-nuclear implementation of the machine-learning classifier tdescore: it judged every transient from light-curve properties alone, using no host-galaxy information at all. The distinguishing marks were a high lower bound on the blackbody temperature and a temperature that rose with time instead of cooling. Because tidal-disruption searches have long been pointed at galactic nuclei, a filter that ignores the host can see exactly what that assumption left outside.[1]
The prosaic explanations were eliminated first. A Type Ia supernova model fitted poorly, with a chi-squared per degree of freedom of 4.5. An active galactic nucleus was ruled out because the host spectrum lacked the diagnostic emission lines. A disruption at the nucleus is incompatible with a 9.3-kiloparsec separation. The expected explanation for a bright point in a galaxy's outskirts is a supernova, and that is the one that had to be killed.[1]
What stays unresolved
How the black hole got there has not been established. It may have been ejected during a galaxy merger; it may sit inside a tidally stripped satellite galaxy. Deciding between them requires late-time observations. Both scenarios produce the same separation, so 9.3 kiloparsecs on its own supports neither; what distinguishes them is whether any other stellar population is found at that position.[1]
Lead author Robert Stein says the technique has been validated and can be used to hunt for more, adding that Rubin's wide, deep surveys will yield a far larger sample than current telescopes can collect. The paper itself concedes that replicating such a discovery is difficult and that confirmation demands expensive follow-up. The testable expectation is this: if within Rubin's first survey year at least one further tidal disruption passes the off-nuclear filter and is confirmed by independent spectroscopy, the gain lies in the method rather than in one lucky source.[1]