Black hole goes with the flow - - Wed 9 Jan 21:37 GMT

Black hole goes with the flow -

Reverberation mapping applied to a stellar-mass black hole.

  In a paper in Nature, Kara et al.1 report observations of an astronomical object discovered last March2,3 known as MAXI J1820 + 070, which consists of a stellar-mass black hole that is collecting (accreting) gas from a companion star through a structure called an accretion disk.

  These results led researchers to develop models that attribute the long reverberation lags to a truncated accretion disk, in which the inner edge of the disk is positioned hundreds of gravitational radii from the black hole (Fig. 1a).

  In these models, the accretion disk evolves over time — the truncation radius gradually becomes smaller when the black hole undergoes an outburst, owing to an increasing accretion rate.

  These reverberation lags mapped the distance between the corona and the inner edge of the accretion disk during the black hole’s transition from outburst back to its normal state (quiescence).

  Second, studies of highly variable active galactic nuclei, in particular those whose supermassive black holes transition rapidly from bright to faint states, or vice versa13–16, would provide valuable tests of whether the structures of accretion disks are similar for stellar-mass and supermassive black holes.