Physical Society Colloquium
Interview for Faculty Position
Magnetic Interaction between a Black Hole and
an
Accretion Disk and Its Observational Signatures
Li-Xin Li
Harvard-Smithsonian Institute
The interaction between a black hole and an accretion disk mediated by a
magnetic field connecting them has been ignored in the standard theory of
accretion disks but has been shown to be important by recent studies. When a
black hole is connected to its accretion disk by a magnetic field - a
configuration that may naturally happen when the disk is magnetized, the
magnetic field transports energy and angular momentum between the black hole
and the disk. If the black hole rotates faster than the disk, the spin energy
of the black hole is extracted by the magnetic field and transported to the
disk, increasing the power of the disk and modifying the spectrum of the
radiation from the disk. If the black hole rotates slower than the disk, the
inner region of the disk is disrupted by the magnetic field, resulting that
the inner boundary of the disk moves outward until a radius is reached where
the angular velocity of the disk is equal to the angular velocity of the
black hole. If the black hole rotates very slowly, the disk will have a very
large inner radius and a very low radiation efficiency. The observational
signatures of the magnetic interaction from recent observations by XMM-Newton
will be discussed.
Thursday, February 26th 2004, 16:00
Ernest Rutherford Physics Building, R.E. Bell Conference Room (room 103)
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