Related papers: Confronting models for the high-frequency QPOs wit…
We measure simultaneously the properties of the energy spectra and the frequencies of the kilohertz quasi-periodic oscillations (QPOs) in fifteen low mass X-ray binaries covering a wide range of X-ray luminosities. In each source the QPO…
We apply the global mode analysis, which has been recently developed for the modeling of kHz quasi-periodic oscillations (QPOs) from neutron stars, to the inner region of an accretion disk around a rotating black hole. Within a…
Kilohertz quasi-periodic oscillations or kHz QPOs occur on the orbital timescale of the inner accretion flow and may carry signatures of the physics of strong gravity (c$^{2}$ ~ GM/R) and possibly clues to constraining the neutron star…
Two inter-related peaks occur in high-frequency power spectra of X-ray lightcurves of several black-hole candidates. We further explore the idea that a non-linear resonance mechanism, operating in strong-gravity regime, is responsible for…
Quasi-Periodic Oscillations (QPOs) are an important phenomenon commonly observed in the X-ray radiation of black holes and neutron stars, closely related to the dynamics of accretion disks around compact objects and general relativistic…
We briefly review the properties and physical consequences of quasiperiodic oscillations (QPOs) seen on many occasions in the X-ray emission from black-hole binary systems. We also report on the discovery of QPOs at 164 and 328 Hz in…
We continue our earlier studies of quasi-periodic oscillations (QPOs) in the power spectra of accreting, rapidly-rotating black holes that originate from the geometric "light echoes" of X-ray flares occurring within the black hole…
We continue to investigate the X-ray timing and spectral properties of the black hole binary, XTE J1550-564. For three different groups of observations, we show evidence that two high-frequency QPOs (HFQPOs) occur simultaneously near 184…
We suggest that persistent low-frequency quasi-periodic oscillations (QPOs) detected in X-ray, ultraviolet, optical energy ranges the black hole (BH) sources XTE J1118+480, GRO J1655-40 LMC X-1 at ~ 0.1 Hz, and QPOs in HZ Her/Her X-1 at ~…
In the Galactic microquasars with double peak kHz quasi-periodic oscillations (QPOs), the ratio of the two frequencies is 3:2. This supports the suggestion that double peak kHz QPOs are due to a non-linear resonance between two modes of…
Quasi-periodic oscillations (QPOs) have been widely observed in black hole X-ray binaries (BHBs), which often exhibit significant X-ray variations. Extensive research has explored the long-term evolution of the properties of QPOs in BHBs.…
Based on the $Insight$-HXMT archival data, we have detected a new atypical low-frequency quasi-periodic oscillation (LFQPO) in the black hole X-ray binary MAXI J1348$-$630. The new LFQPO is detected in all the three instruments of…
Type-C quasi-periodic oscillations (QPOs) are the low-frequency QPOs most commonly observed during the hard spectral state of X-ray binary systems. The leading model for these QPOs is the Lense-Thirring precession of a hot, geometrically…
A recent study of the X-ray source XMMUJ134736.6+173403 has revealed a strong quasi-periodic modulation of the X-ray flux. The observation of two quasiperiodic oscillations (QPOs) that occur on a daily timescale and exhibit a 3:1 frequency…
In the context of high-frequency quasi-periodic oscillation (HF QPOs) we further explore the appearance of an observable signal generated by hot spots moving along quasi-elliptic trajectories close to the innermost stable circular orbit in…
This investigation examines QPOs in two quantum-corrected BH spacetimes that preserve general covariance while incorporating quantum gravitational effects through a dimensionless parameter \zeta. We combine analytical derivations of…
Origin of wide varieties of quasi-periodic oscillation (QPO) observed in compact sources is still not well established. Its frequencies range from mHz to kHz spanning all compact objects. Are different QPOs, with different frequencies,…
We ascribe the interpretation of the twin kilohertz Quasi Periodic Oscillations (kHz QPOs) of X-ray spectra of Low Mass X-Ray Binaries (LMXBs) to MHD Alfven wave oscillations in the different mass density regions of the accreted matter at…
This study examines the combined effect of electric charge and Lorentz symmetry breaking (LSB) on the observables of strong gravitational lensing (SGL) and the dynamics of quasiperiodic oscillations (QPOs) around an electrically charged,…
We present a study of the complex phase lag behavior of the low-frequency (<20 Hz) quasi-periodic oscillations (QPOs) in the X-ray transient and black-hole candidate XTE J1550-564 during its very high state. We distinguish two different…