Relativistic simulation of flip-flop instabilities of Bondi-Hoyle accretion and quasi-periodic oscillations

Abstract

It is known from recent numerical calculations that Bondi-Hoyle accretion creates a shock cone behind compact objects. This type of accretion leads to instabilities, which can explain certain astrophysical phenomena. In this paper, our main goal is to find the flip-flop behaviour of the shock cone in the relativistic region. In order to do so we have modelled the dynamics of a shock cone around non-rotating and rotating black holes at the equatorial plane in 2D. The effects of the various parameters on the shock cones and instabilities, such as the asymptotic velocity, sound speed, Mach number and adiabatic index, are studied. We have determined the mass accretion rate, shock opening angle, shock cone oscillation, quasi-periodic oscillations (QPOs), and growth rate of instabilities to reveal the disc properties and its radiation. We have discovered, for the first time, flip-flop instabilities around a black hole in the relativistic region by solving the general relativistic hydrodynamical equations. The flip-flop instabilities are found for sound speeds C s,∞ < 0.2 with moderate Mach numbers (∼M = 3 and M = 4 for C s,∞ = 0.1 or M = 7 and M = 8 for C s,∞ = 0.05). Our calculation clearly confirms that the shock cone should be detached from the black hole in the Bondi-Hoyle accretion flow with ≥ 2 for non-rotating and rotating black holes. Results reveal that the flip-flopping shock cone not only creates a torque effect on the black hole but also produces continuous X-ray flares with a certain frequency. Furthermore, QPOs originate inside the shock cone and are stronger in regions that have a radius of a few gravitational radii away from the centre owing to the flip-flop oscillation. Finally, our results are compared with the results of numerical and theoretical calculations in Newtonian hydrodynamics, and it is found that they are in good agreement.

Dynamical Evolution of the Shock Cone around $4D$ Einstein-Gauss Bonnet Rotating Black Hole

“…The High Resolution Shock Capturing (HRSC) scheme is used to solve Eq.9 along with Marquina fluxes, and MUSCL left and right states of the primitive variables at each cell center (Dönmez 2004;Donmez 2006;Dönmez 2012).…”

“…There were other studies in 2D and 3D accomplished recently (Foglizzo et al 2005;Blondin 2013;MacLeod & Ramirez-Ruiz 2015;Ohsugi 2018;Xu & Stone 2019). BHL accretion around the black hole was extensively studied using the general relativistic hydrodynamics and magneto-hydrodynamics either in case of spherical symmetry or axial symmetry (Dönmez et al 2011;Penner 2011;Dönmez 2012;Penner 2012;Lora-Clavijo & Guzmán 2013;Lora-Clavijo et al 2015;Cruz-Osorio & Lora-Clavijo 2016). Studying BHL accretion onto the rotating black hole using the modified gravity may specify more information about the rotating black hole.…”

Investigating the instability of the torus around the blackhole in the presence of the radial and angular velocity perturbations

“…On the other hand, the observed peaks around the rotating black hole-torus system are more powerful and the 3:2 ratio occurs in the oscillating torus due to overtone and nonlinear coupling of the overtones. The nonlinear coupling may be an important excitation mechanism of the X-ray flares [10,20,[23][24][25]33].…”

Relativistic Bondi–Hoyle–Lyttleton accretion in the presence of small rigid bodies around a black hole

“…In the present work, we show, for the first time, a model of the relativistic BHL accretion of hot gas, in the presence of small obstacles around the accretor. In the astrophysical context, relativistic BHL accretion has been used to study different processes, from the vibrations in the shock cone, which may potentially explain high energy phenomena like QPOs (Dönmez et al 2011;Dönmez 2012;, to ultra-relativistic processes associated with the growth of primordial BHs during the radiation era (Penner 2013;Cruz-Osorio et al 2013). Given the importance of understanding the accretion process, the relativistic BHL problem has also been studied in the presence of magnetic fields (Penner 2011), radiative terms (Zanotti et al 2011), and with density or velocity gradients (Lora-Clavijo et al 2015b;Cruz-Osorio & Lora-Clavijo 2016).…”