Related papers: Wavelet Analysis of AGN X-Ray Time Series: A QPO i…

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…

The quasi-periodic oscillations (QPOs) found in active galactic nuclei (AGNs) are a very interesting observational phenomenon implying an unknown physical mechanism around supermassive black holes. Several AGNs have been found to have QPO…

Quasi-periodic oscillation (QPO) detected in the X-ray radiation of black hole X-ray binaries (BHXBs) is thought to originate from dynamical processes in the close vicinity of the black holes (BHs), and thus carries important physical…

Context: 3C 273, a well-studied active galactic nucleus (AGN), displays characteristics of both jetted-AGN and Seyfert galaxies, making it an excellent source to study the disc-jet connection in AGN. Aims: To investigate the disk-jet…

The discovery of 3:2 quasi-periodic oscillations (QPOs) in the ultraluminous X-ray source NGC 1313 X-1 suggests it harbors an intermediate-mass black hole (IMBH). We test this numerically by modelling the 3:2 QPOs and the associated X-ray…

Very few galactic nuclei are found to show significant X-ray quasi-periodic oscillations (QPOs). After carefully modeling the noise continuum, we find that the ~3.8 hr QPO in the ultrasoft active galactic nucleus (AGN) candidate 2XMM…

Quasi-periodic oscillations and X-ray spectroscopy are powerful probes of black hole masses and accretion disks, and here we apply these diagnostics to an ultraluminous X-ray source (ULX) in the spiral galaxy NGC628 (M74). This object was…

Quasars show a remarkable degree of atomic emission line-broadening, an observational feature which, in conjunction with a radial distance estimate for this emission from the nucleus is often used to infer the mass of the central…

Observation of the bright Seyfert 1 galaxy RE J1034+396 is believed to demonstrate a drift of the central period of the Quasi Periodic Oscillation (QPO) linearly correlated with the temporary X-ray luminosity. We show, using a specific…

We detected a possible quasi-periodic oscillation (QPO) of ~ 71 days in the 0.1 -- 300 GeV gamma-ray Fermi-LAT light curve of the high redshift flat spectrum radio quasar B2 1520+31. We identify and confirm that quasi-period by Lomb Scargle…

RX J1301.9+2747 is an ultrasoft active galactic nucleus (AGN) with unusual X-ray variability that is characterized by a long quiescent state and a short-lived flare state. The X-ray flares are found to recur quasi-periodically on a…

Quasiperiodic oscillations (QPOs) in active galactic nuclei (AGNs) provide a powerful tool for probing the structure of the innermost accretion flow and corona around supermassive black holes. RE~J1034+396, the most prominent AGN known to…

We present a model that explains some extreme variability phenomena observed in active galactic nuclei (AGN). In this model, an orbiting companion interacts with the accretion disk surrounding the central supermassive black hole (SMBH).…

X-ray timing of active galactic nuclei (AGN) provides a unique probe of gas accretion onto supermassive black holes (SMBHs). Quasi-periodic oscillations (QPOs), which trace gas dynamics in the strongly curved spacetime around SMBHs, are…

Quasi-periodic eruptions (QPEs) are rapid, recurring X-ray bursts from supermassive black holes, believed to result from interactions between accretion disks and surrounding matter. The galaxy SDSS1335+0728, previously stable for two…

[Abridged] Optically thick, geometrically thin accretion disks around supermassive black holes are thought to contribute to broad-line emission in type-1 active galactic nuclei (AGN). However, observed emission line profiles most often…

X-ray quasi-periodic oscillations (QPOs) in AGN allow us to probe and understand the nature of accretion in highly curved space-time, yet the most robust form of detection (i.e. repeat detections over multiple observations) has been limited…

Recent X-ray observations by Jiang et al. have identified an active galactic nucleus (AGN) in the bulgeless spiral galaxy NGC 3319, located just $14.3\pm1.1\,$Mpc away, and suggest the presence of an intermediate-mass black hole (IMBH;…

In this paper we apply the reverberation method to determine the mass of the black hole in 3C273 from the Ly a and C iv emission lines using archival IUE observations. Following the standard assumptions of the method, we find a…

Recent X-ray observations have revealed growing evidence of quasi-periodic oscillation (QPO) in the light curve of active galactic nuclei (AGNs), which may serve as a useful probe of black hole physics. In this work, we present a systematic…