A model for 3:2 HFQPO pairs in black hole binaries based on cosmic battery

Abstract

A model for 3:2 high-frequency quasi-periodic oscillations (HFQPOs) with 3:2 pairs observed in four black hole X-ray binaries (BHXBs) is proposed by invoking the epicyclic resonances with the magnetic connection (MC) between a spinning black hole (BH) with a relativistic accretion disc. It turns out that the MC can be worked out due to Poynting-Robertson cosmic battery (PRCB), and the 3:2 HFQPO pairs associated with the steep power-law states can be fitted in this model. Furthermore, the severe damping problem in the epicyclic resonance model can be overcome by transferring energy from the BH to the inner disc via the MC process for emitting X-rays with sufficient amplitude and coherence to produce the HFQPOs. In addition, we discuss the important role of the magnetic field in state transition of BHXBs.

Estimating the black hole mass of NGC1313 X-1 based on the spectral and timing properties

“…As suggested by Kylafis et al (2012), the current is generated near the innermost stable circular orbit (ISCO) of the disk. Fitting the 3:2 HFQPO pairs and the associated spectrum from BHXBs by Huang et al (2016) also indicates that the current is very near the ISCO. For simplicity, We set r PRCB = 1.01r ISCO in this work, where r ISCO is the radius of ISCO.…”

“…In the PRCB scenario, electrons in the inner accretion disk feel a much stronger radiation-drag force than the ions due to a much larger Thompson cross-section leading to an electric current loop generated near the inner edge of the accretion disk. The current intensity can be estimated as (Huang et al, 2016)…”

“…where ∆t and ∆S are the average scattering time of electrons with photons and the cross-section of the current, respectively, F is the radiation flux from the relativistic accretion disk (Novikov & Thorne, 1973;Page & Thorne, 1974), n is the number density of electrons, v k is the Kepler velocity, σ T is the Thompson cross-section and e is the electric quality of an electron. Following Huang et al (2016), we set ∆t = 10 −9 s and ∆S = (0.01M BH ) 2 , where M BH is the BH mass. The values of F , n and v k are all evaluated at the radius r PRCB where the current is generated.…”

“…The magnetic fields generated by the PRCB current can be calculated in the frame of general relativity (Linet, 1979;Li, 2002b). As shown in Huang et al (2016), two types of MC configurations are created by the PRCB current with one connecting the BH horizon and the disk and the other connecting the plunging region and the inner disk. The rotational energy of both the BH and the plunging region can be transferred to the inner disk by these two MC processes.…”

“…However, quantitative and numerical analyses are needed to test this result. In this paper, we estimate the BH mass in NGC 1313 X-1 by modelling the 3:2 QPOs and the associated X-ray spectrum simultaneously based on the epicyclic resonance model (ERM) and a magnetic disk-corona model developed by Huang et al (2016).…”