GRS 1915+105 is an X-ray binary containing an accreting stellar-mass black hole. Gas supplied by its companion forms an accretion disk; changes in that gas produce strong, variable X-ray emission. Its radio-emitting jets make it an example of a microquasar.
The thermal disk spectrum has been used to estimate the black-hole spin by fitting a relativistic disk model. The inference depends on quantities including mass, distance, inclination and the disk's physical state. It therefore illustrates how a bright spectrum constrains a compact object through a model, rather than providing a direct measurement of the event horizon.[ref]
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