scholarly journals Tidal Interaction between a Fluid Star and a Kerr Black Hole in Circular Orbit

2000 ◽  
Vol 532 (1) ◽  
pp. 530-539 ◽  
Author(s):  
Paul Wiggins ◽  
Dong Lai
Keyword(s):  
Black Hole ◽  
Circular Orbit ◽  
Kerr Black Hole ◽  
Tidal Interaction

scholarly journals Detection of orbital motions near the last stable circular orbit of the massive black hole SgrA*

2018 ◽  
Vol 618 ◽  
pp. L10 ◽  
Author(s):  
◽  
R. Abuter ◽  
A. Amorim ◽  
M. Bauböck ◽  
J. P. Berger ◽  
...  
Keyword(s):  
Black Hole ◽  
Circular Orbit ◽  
Near Infrared ◽  
Hot Spot ◽  
Kerr Black Hole ◽  
Polarization Angle ◽  
Gravitational Radius ◽  
Massive Black Hole ◽  
Poloidal Magnetic Field ◽  
Continuous Rotation

We report the detection of continuous positional and polarization changes of the compact source SgrA* in high states (“flares”) of its variable near-infrared emission with the near-infrared GRAVITY-Very Large Telescope Interferometer (VLTI) beam-combining instrument. In three prominent bright flares, the position centroids exhibit clockwise looped motion on the sky, on scales of typically 150 μas over a few tens of minutes, corresponding to about 30% the speed of light. At the same time, the flares exhibit continuous rotation of the polarization angle, with about the same 45(±15) min period as that of the centroid motions. Modelling with relativistic ray tracing shows that these findings are all consistent with a near face-on, circular orbit of a compact polarized “hot spot” of infrared synchrotron emission at approximately six to ten times the gravitational radius of a black hole of 4 million solar masses. This corresponds to the region just outside the innermost, stable, prograde circular orbit (ISCO) of a Schwarzschild–Kerr black hole, or near the retrograde ISCO of a highly spun-up Kerr hole. The polarization signature is consistent with orbital motion in a strong poloidal magnetic field.

Black Hole Spin

2014 ◽  
Author(s):  
Charles D. Bailyn
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Accretion Disk ◽  
Circular Orbit ◽  
Kerr Black Hole ◽  
Schwarzschild Black Hole ◽  
Physical Size ◽  
Stable Circular Orbit ◽  
Innermost Stable Circular Orbit

This chapter examines the spin of a black hole. The spin is usually described as a nondimensional parameter, which can range from zero (a nonspinning black hole) to one (a situation described as “maximally spinning”). The differences in space-time between a nonspinning Schwarzschild black hole and a Kerr black hole of the same mass have potentially observable effects. The most obvious of these differences is the position of the innermost stable circular orbit (ISCO), which has a significant effect on the inner edge of an accretion disk. It is through determination of the physical size of the ISCO that the spins of black holes are determined.

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