Corotational Instability, Magnetic Resonances and Global Inertial-Acoustic Oscillations in Magnetized Black-Hole Accretion Discs

Low-order, non-axisymmetric p-modes (also referred as inertial-acoustic modes) trapped in the inner-most region of hydrodynamic accretion discs around black holes, are plausible candidates for high-frequency quasi-periodic oscillations (QPOs) observed in a number of accreting black-hole systems. These modes are subject to global instabilities due to wave absorption at the corotation resonance (where the wave pattern frequency $\omega/m$ equals the disc rotation rate $\Omega$), when the fluid vortensity, $\zeta=\kappa^2/(2\Omega\Sigma)$ (where $\kappa$ and $\Sigma$ are the radial epicyclic frequency and disc surface density, respectively), has a positive gradient. We investigate the effects of disc magnetic fields on the wave absorption at corotation and the related wave super-reflection of the corotation barrier, and on the overstability of disc p-modes. For discs with a pure toroidal field, the corotation resonance is split into two magnetic resonances, where the wave frequency in the corotating frame of the fluid, $\tomega=\omega-m\Omega$, matches the slow magnetosonic wave frequency. Significant wave energy/angular momentum absorption occurs at both magnetic resonances, but with opposite signs. The combined effect of the two magnetic resonances is to reduce the super-reflection and the growth rate of the overstable p-modes. We show that even a subthermal toroidal field may suppress the overstability of hydrodynamic (B=0) p-modes. For accretion discs with mixed (toroidal and vertical) magnetic fields, two additional Alfven resonances appear, where $\tomega$ matches the local Alfven wave frequency. They further reduce the growth rate of p-modes. Our results suggest that in order for the non-axisymmetric p-modes to be a viable candidate for the observed high-frequency QPOs, the disc magnetic field must be appreciably subthermal, or other mode excitation mechanisms are at work.

Comments: 21 pages, 11 figures, MNRAS accepted

Similar Publications

Electrons at relativistic speeds, diffusing in magnetic fields, cause copious emission at radio frequencies in both clusters of galaxies and radio galaxies, through the non-thermal radiation emission called synchrotron. However, the total power radiated through this mechanism is ill constrained, as the lower limit of the electron energy distribution, or low-energy cutoffs, for radio emission in galaxy clusters and radio galaxies have not yet been determined. This lower limit, parametrized by the lower limit of the electron momentum - pmin - is critical for estimating the energetics of non-thermal electrons produced by cluster mergers or injected by radio galaxy jets, which impacts the formation of large-scale structure in the universe, as well as the evolution of local structures inside galaxy clusters. Read More

The abundance of accelerators and the ambient conditions make Cygnus X a natural laboratory for studying the life cycle of cosmic-rays (CRs). This naturally makes the Cygnus X complex a highly interesting source in neutrino astronomy, in particular concerning a possible detection with the IceCube Neutrino Observatory, which has a good view of the northern hemisphere. In this paper, we model the multiwavelength spectrum of the Cygnus, for the first time using a broad data set from radio, MeV (COMPTEL), GeV (Fermi), TeV (Argo) and 10s of TeV (Milagro) energies. Read More

Authors: A. Aduszkiewicz, Y. Ali, E. V. Andronov, T. Antićić, B. Baatar, M. Baszczyk, S. Bhosale, A. Blondel, M. Bogomilov, A. Brandin, A. Bravar, J. Brzychczyk, S. A. Bunyatov, O. Busygina, H. Cherif, M. Ćirković, T. Czopowicz, A. Damyanova, N. Davis, H. Dembinski, M. Deveaux, W. Dominik, P. Dorosz, J. Dumarchez, R. Engel, A. Ereditato, S. Faas, G. A. Feofilov, Z. Fodor, C. Francois, A. Garibov, X. Garrido, M. Gaździcki, M. Golubeva, K. Grebieszkow, F. Guber, A. Haesler, A. E. Hervé, J. Hylen, S. N. Igolkin, A. Ivashkin, S. R. Johnson, K. Kadija, E. Kaptur, M. Kiełbowicz, V. A. Kireyeu, V. Klochkov, V. I. Kolesnikov, D. Kolev, A. Korzenev, V. N. Kovalenko, K. Kowalik, S. Kowalski, M. Koziel, A. Krasnoperov, W. Kucewicz, M. Kuich, A. Kurepin, D. Larsen, A. László, T. V. Lazareva, M. Lewicki, B. Lundberg, B. Łysakowski, V. V. Lyubushkin, M. Maćkowiak-Pawłowska, B. Maksiak, A. I. Malakhov, D. Manić, A. Marchionni, A. Marcinek, A. D. Marino, I. C. Mariş, K. Marton, H. -J. Mathes, T. Matulewicz, V. Matveev, G. L. Melkumov, A. O. Merzlaya, B. Messerly, Ł. Mik, G. B. Mills, S. Morozov, S. Mrówczyński, Y. Nagai, M. Naskręt, V. Ozvenchuk, V. Paolone, M. Pavin, O. Petukhov, C. Pistillo, R. Płaneta, P. Podlaski, B. A. Popov, M. Posiadała, S. Puławski, J. Puzović, R. Rameika, W. Rauch, M. Ravonel, R. Renfordt, E. Richter-Wąs, D. Röhrich, E. Rondio, M. Roth, M. Ruprecht, B. T. Rumberger, A. Rustamov, M. Rybczynski, A. Rybicki, A. Sadovsky, K. Schmidt, I. Selyuzhenkov, A. Yu. Seryakov, P. Seyboth, M. Słodkowski, A. Snoch, P. Staszel, G. Stefanek, J. Stepaniak, M. Strikhanov, H. Ströbele, T. Šuša, M. Szuba, A. Taranenko, A. Tefelska, D. Tefelski, V. Tereshchenko, A. Toia, R. Tsenov, L. Turko, R. Ulrich, M. Unger, F. F. Valiev, D. Veberič, V. V. Vechernin, M. Walewski, A. Wickremasinghe, C. Wilkinson, Z. Włodarczyk, A. Wojtaszek-Szwarc, O. Wyszyński, L. Zambelli, E. D. Zimmerman, R. Zwaska

We present measurements of $\rho^0$, $\omega$ and K$^{*0}$ spectra in $\pi^{-} + $C production interactions at 158 GeV/c and $\rho^0$ spectra at 350 GeV/c using the NA61/SHINE spectrometer at the CERN SPS. Spectra are presented as a function of the Feynman's variable $x_\text{F}$ in the range $0 < x_\text{F} < 1$ and $0 < x_\text{F} < 0.5$ for 158 GeV/c and 350 GeV/c respectively. Read More

The neutrino burst detected during supernova SN1987A is explained in a strangeon star model, in which it is proposed that a pulsar-like compact object is composed of strangeons (strangeon: an abbreviation of "strange nucleon"). A nascent strangeon star's initial internal energy is calculated, with the inclusion of pion excitation (energy around 10^53 erg, comparable to the gravitational binding energy of a collapsed core). A liquid-solid phase transition at temperature ~ 1-2 MeV may occur only a few ten-seconds after core-collapse, and the thermal evolution of strangeon star is then modeled. Read More

We describe a new analytical model for the accretion of particles from a rotating and charged spherical shell of dilute collisionless plasma onto a rotating and charged black hole. By assuming a continuous injection of particles at the spherical shell and by treating the black hole and a featureless accretion disc located in the equatorial plane as passive sinks of particles we build a stationary accretion model. This may then serve as a toy model for plasma feeding an accretion disc around a charged and rotating black hole. Read More

We report on the first experimental observation of a current-driven instability developing in a quasi-neutral matter-antimatter beam. Strong magnetic fields ($\geq$ 1 T) are measured, via means of a proton radiography technique, after the propagation of a neutral electron-positron beam through a background electron-ion plasma.The experimentally determined equipartition parameter of $\epsilon_B \approx 10^{-3}$, is typical of values inferred from models of astrophysical gamma-ray bursts, in which the relativistic flows are also expected to be pair dominated. Read More

We examine the effects of a global magnetic field and outflow on radiatively inefficient accretion flow (RIAF) in the presence of magnetic resistivity. We find a self-similar solutions for the height integrated equations that govern the behavior of the flow. We use the mixing length mechanism for studying the convection parameter. Read More

We present a one-parameter family of stationary, asymptotically flat solutions of the Einstein-Maxwell equations with only a mild singularity, which are endowed with mass, angular momentum, a dipole magnetic moment and a quadrupole electric moment. We briefly analyze the structure of this solution, which we interpret as a system of two extreme co-rotating black holes with equal masses and electric charges, and opposite magnetic and gravimagnetic charges, held apart by an electrically charged, magnetized string which also acts as a Dirac-Misner string. Read More

Understanding the origin of the flaring activity from the Galactic center supermassive black hole, Sagittarius A*, is a major scientific goal of the NuSTAR Galactic plane survey campaign. We report on the data obtained between July 2012 and April 2015, including 27 observations on Sgr A* with a total exposure of ~ 1 Ms. We found a total of ten X-ray flares detected in the NuSTAR observation window, with luminosities in the range of $L_{3-79~keV}$~$(0. Read More