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تسجيل مستخدم جديدA Phase Lag between Disk and Corona in GRMHD Simulations of Precessing Tilted Accretion Disks
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In the course of its evolution, a black hole (BH) accretes gas from a wide range of directions. Given a random accretion event, the typical angular momentum of an accretion disc would be tilted by $sim$60$^circ$ relative to the BH spin. Misalignment causes the disc to precess at a rate that increases with BH spin and tilt angle. We present the first general-relativistic magnetohydrodynamic (GRMHD) simulations spanning a full precession period of highly tilted (60$^circ$), moderately thin ($h/r=0.1$) accretion discs around a rapidly spinning ($asimeq0.9$) BH. While the disc and jets precess in phase, we find that the corona, sandwiched between the two, lags behind by $gtrsim 10^{circ}$. For spectral models of BH accretion, the implication is that hard non-thermal (corona) emission lags behind the softer (disc) emission, thus potentially explaining some properties of the hard energy lags seen in Type-C low frequency quasi-periodic oscillations in X-Ray binaries. While strong jets are unaffected by this disc-corona lag, weak jets stall when encountering the lagging corona at distances $r sim 100$ black hole radii. This interaction may quench large-scale jet formation.
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