“A mysterious object has been spotted that’s 10 million times as bright as the sun. Scientists can’t work out why it hasn’t exploded. Ultraluminous X-ray sources are objects that shine 10 million times as bright as the sun. Scientists have said they are too bright to exist, as they break the Eddington limit. A new study confirmed the brightness of a ULX — leaving the mystery of how it exists unsolved.”
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“NASA Study Helps Explain Limit-Breaking Ultra-Luminous X-Ray Sources. These objects are more than 100 times brighter than they should be. Observations by the agency’s NuSTAR X-ray telescope support a possible solution to this puzzle.”
“Orbital Decay in M82 X-2“—”M82 X-2 is the first pulsating ultraluminous X-ray source discovered. The luminosity of these extreme pulsars, if isotropic, implies an extreme mass transfer rate. An alternative is to assume a much lower mass transfer rate, but with an apparent luminosity boosted by geometrical beaming. Only an independent measurement of the mass transfer rate can help discriminate between these two scenarios. In this paper, we follow the orbit of the neutron star for 7 yr, measure the decay of the orbit […] and argue that this orbital decay is driven by extreme mass transfer of more than 150 times the mass transfer limit set by the Eddington luminosity. If this is true, the mass available to the accretor is more than enough to justify its luminosity, with no need for beaming. This also strongly favors models where the accretor is a highly magnetized neutron star.”