scholarly journals Drop of coherence of the lower kilo-Hz QPO in neutron stars: Is there a link with the innermost stable circular orbit?

2005 ◽  
Vol 326 (9) ◽  
pp. 808-811 ◽  
Author(s):  
D. Barret ◽  
J.-F. Olive ◽  
M. Coleman Miller
Keyword(s):  
Neutron Stars ◽  
Circular Orbit ◽  
Stable Circular Orbit ◽  
Innermost Stable Circular Orbit

scholarly journals Lyapunov exponent, ISCO and Kolmogorov–Senai entropy for Kerr–Kiselev black hole

2021 ◽  
Vol 81 (1) ◽  
Author(s):  
Monimala Mondal ◽  
Farook Rahaman ◽  
Ksh. Newton Singh
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Lyapunov Exponent ◽  
Circular Orbit ◽  
Real Root ◽  
Angular Frequency ◽  
Geodesic Motion ◽  
Radial Equation ◽  
Stable Circular Orbit ◽  
Innermost Stable Circular Orbit

AbstractGeodesic motion has significant characteristics of space-time. We calculate the principle Lyapunov exponent (LE), which is the inverse of the instability timescale associated with this geodesics and Kolmogorov–Senai (KS) entropy for our rotating Kerr–Kiselev (KK) black hole. We have investigate the existence of stable/unstable equatorial circular orbits via LE and KS entropy for time-like and null circular geodesics. We have shown that both LE and KS entropy can be written in terms of the radial equation of innermost stable circular orbit (ISCO) for time-like circular orbit. Also, we computed the equation marginally bound circular orbit, which gives the radius (smallest real root) of marginally bound circular orbit (MBCO). We found that the null circular geodesics has larger angular frequency than time-like circular geodesics ($$Q_o > Q_{\sigma }$$ Q o > Q σ ). Thus, null-circular geodesics provides the fastest way to circulate KK black holes. Further, it is also to be noted that null circular geodesics has shortest orbital period $$(T_{photon}< T_{ISCO})$$ ( T photon < T ISCO ) among the all possible circular geodesics. Even null circular geodesics traverses fastest than any stable time-like circular geodesics other than the ISCO.

Magnetic field and radius of the innermost stable circular orbit near super-massive black holes in active galactic nuclei

2015 ◽  
Vol 336 (10) ◽  
pp. 1013-1016 ◽  
Author(s):  
M. Yu. Piotrovich ◽  
Yu. N. Gnedin ◽  
N. A. Silant'ev ◽  
T. M. Natsvlishvili ◽  
S. D. Buliga
Keyword(s):  
Magnetic Field ◽  
Black Holes ◽  
Active Galactic Nuclei ◽  
Circular Orbit ◽  
Galactic Nuclei ◽  
Massive Black Holes ◽  
Stable Circular Orbit ◽  
Innermost Stable Circular Orbit
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