Testing black holes in non-linear electrodynamics from the observed quasi-periodic oscillations

Abstract

Quasi-periodic oscillations (QPOs), in particular, the ones with high frequencies, often observed in the power spectrum of black holes, are useful in understanding the nature of strong gravity since they are associated with the motion of matter in the vicinity of the black hole horizon. Interestingly, these high frequency QPOs (HFQPOs) are observed in commensurable pairs, the most common ratio being 3:2. Several theoretical models are proposed in the literature which explain the HFQPOs in terms of the orbital and epicyclic frequencies of matter rotating around the central object. Since these frequencies are sensitive to the background spacetime, the observed HFQPOs can potentially extract useful information regarding the nature of the same. In this work, we investigate the role of regular black holes with a Minkowski core, which arise in gravity coupled to non-linear electrodynamics, in explaining the HFQPOs. Regular black holes are particularly interesting as they provide a possible resolution to the singularity problem in general relativity. We compare the model dependent QPO frequencies with the available observations of the quasi-periodic oscillations from black hole sources and perform a χ2 analysis. Our study reveals that most QPO models favor small but non-trivial values of the non-linear electrodynamics charge parameter. In particular, black holes with large values of non-linear electrodynamics charge parameter are generically disfavored by present observations related to QPOs.

Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A ∗

“…The GCSV BH was introduced in [351][352][353], including work by one of us, as toy model of a regular BH in the sense of Bardeen, where the core is asymptotically Minkowski rather than de Sitter 33 : stated differently, the associated energy density and pressure asymptote to zero rather than to a final value determined by the effective cosmological constant of the de Sitter case (see also [131,[354][355][356][357][358][359][360][361][362]). While the GCSV BH is introduced in a purely phenomenological way, Simpson and Visser (SV) argued in [353] that this space-time is mathematically interesting due to its tractability (the curvature tensors and invariants take forms which are much simpler than those of the Bardeen, Hayward, and Frolov BHs), and physically interesting because of its non-standard asymptotically Minkowski core.…”

On the Parameters of the Spherically Symmetric Parameterized Rezzolla–Zhidenko Spacetime through Solar System Tests, the Orbit of the S2 Star about Sgr A*, and Quasiperiodic Oscillations

“…To confirm what we obtained through observational data for star S2, we also considered observational data in the close vicinity of the black hole, i.e., M/r + ∼ 10 −1 was always satisfied, which is comparable with the orbit of star S2 around Sgr A å . Therefore, we studied the epicyclic motions and derived the analytic form of the epicyclic frequencies used to constrain these expansion parameters of PRZ spacetime by applying data of the selected microquasars that are well-known as astrophysical QPOs, which are interesting tools for testing and constraining the geometry of metric fields because, as noted in Banerjee (2022), their frequencies solely depend on the spacetime metric and not on the details of the accretion process. Even the radius of the ISCO where accretion occurs only depends on the background metric, provided the energymomentum tensor of the fluid is seen as a test matter.…”

“…For the case of the spherically symmetric metric we are considering in this work, Equations (1), (11), and (12), we have Rebusco 2004;Deligianni et al 2021;Banerjee 2022) are parametric resonance, forced resonance, and Keplerian resonance. There are other models as well (Banerjee 2022).…”

“…We know from previous studies (Kološ et al 2015) that parametric resonance is not able to justify the two twin peaks at 300 Hz and 450 Hz if the GRO J1655-40 microquasar is modeled by a Schwarzschild black hole unless the effects of a magnetic field surrounding the black hole are taken into consideration. Thus, we opt for forced resonance (Deligianni et al 2021;Banerjee 2022) with the model…”

Constraints on the rotating self-dual black hole with quasi-periodic oscillations

“…This field has been explored in many works from the theoretical point of view. For instance, testing the no-hair theorem with GRO J1655-40 [60], studying a black hole in non-linear electrodynamics [61] or the nature of the black hole candidate [62,63], investigating the QPO behaviors around rotating wormholes [64,65], testing gravity with the different kinds of modified gravity theories [66][67][68][69], etc. Although there is still a lack of comparison between the observation of X-ray QPOs and the theory included the effects of LQG.…”