Dynamics of Test Particles and Twin Peaks QPOs around Regular Black Holes in Modified Gravity

Abstract

In this work, we have presented a detailed analysis of the event horizon of regular black holes (BHs) in modified gravity known as MOG, the so-called regular MOG BH. The motion of neutral particles around the BH has also been explored. The test particle motion study shows that the positive (negative) values of the MOG parameter mimic the spin of a rotating Kerr BH, providing the same values for the innermost stable pro-grade (retrograde) orbits of the particles in the range of the spin parameter a/M∈(−0.4125,0.6946). The efficiency of energy release from the accretion disk by the Novikov–Thorne model has been calculated, and the efficiency was shown to be linearly proportional to the increase of the MOG parameter α. Moreover, we have developed a new methodology to test gravity theories in strong-field regimes using precision data from twin-peaked quasiperiodic oscillations (QPOs) of objects calculating possible values of upper and lower frequencies. However, it is obtained that the positive MOG parameter can not mimic the spin of Kerr BHs in terms of the same QPO frequencies. We have provided possible ranges for upper and lower frequencies of twin-peak QPOs with the ratio of the upper and lower frequencies of 3:2 around regular MOG BHs in the different models. Moreover, as an example, we provide detailed numerical analysis of the QPO of GRS 1915+105 with the frequencies νU=168±5Hz and νL=113±3Hz. It is shown that the central BH of the QPO object can be a regular MOG BH when the value of the parameter is α=0.2844−0.1317+0.0074 and shines in the orbits located at the distance r/M=7.6322−0.0826+0.0768 from the central BH. It is also shown that the orbits where QPOs shine are located near the innermost stable circular orbit (ISCO) of the test particle. The correlation between the radii of ISCO and the QPO orbits is found, and it can be used as a new theoretical way to determine ISCO radius through observational data from the QPOs around various compact objects.

Quasiperiodic oscillations from noncommutative inspired black holes

“…Studies of the QPOs can be one of the observational ways to measure the inner edge of an accretion disk around such central compact objects. Recent theoretical models and analyses of observational studies have shown that the orbits where the QPOs are generated, close to the ISCO of the particles [30,59,60]. In other words, the QPO phenomena can play a powerful tool that may allow estimating (approximate) values of the radii of innermost regions of accretion disks and their masses (and radius), and spin of the central compact objects.…”

“…Here the total mass of the BH is taken, as a test value, to be M = 10M . around the BH, such as QPOs [32,60,66]. In such cases, it is quite complicated to distinguish the central BH type.…”

“…The QPO object called GRS 1915-105 have been observed in the frequency band 168 ± 5 Hz and 113 ± 3 Hz [60]. In order to find the radius of the orbit where the QPO shine, we set the equations (168 ± 5)ν L (M, r, Θ) = (113 ± 3)ν U (M, r, Θ), then we solve them numerically, and obtain r/M = 6.72 ± 0.12 and r/M = 7.929 ± 0.025 in the RP and WD models, respectively.…”

Quasiperiodic Oscillations and Dynamics of Test Particles around Quasi- and Non-Schwarzschild Black Holes

“…Fortunately, astrophysical black holes can be mainly observed by the radiation luminosity of the accretion disk, in particular by quasiperiodic oscillation (QPO) frequencies with the ratio 3:2 [6,7]. Using QPOs it is possible to obtain information about spacetime around the black holes and constraints on their total mass, charge, and spin parameters estimated, e.g., in [8][9][10][11][12].…”

Optical Features of AdS Black Holes in the Novel 4D Einstein-Gauss-Bonnet Gravity Coupled to Nonlinear Electrodynamics

“…The internal magnetic fields are crucial due to the magneto-rotational instability generating the disks' viscosity causing accretion itself, while the external magnetic fields could substantially modify the structure of the disk and create non-equatorial charged-particle circular orbits [61]. Motivated by specific interesting properties of the accretion disk, much research has been undertaken, including accretion disks surrounding a BH as a source of QPO in different models [62][63][64], studying the efficiency of energy release from the accretion disk [65], images of the Kaluza-Klein black hole surrounded with thin accretion disk [66] and influence of cosmic repulsion and magnetic fields on accretion disks [67].…”