Related papers: A transient variable 6 Hz QPO from GX 339-4

We found a strong QPO feature at 0.085+/-0.002 Hz in the power spectrum of X-ray transient XTE J1118+480. The QPO was detected in PCA/RXTE data with an amplitude close to 10% rms, and the width 0.034+/-0.006 Hz. The shape of the power…

We have re-analyzed archival RXTE data of the X-ray binary Cygnus X-3 with a view to investigate the timing properties of the source. As compared to previous studies, we use an extensive sample of observations that include all the…

We report the discovery ($20\sigma$) of kilohertz quasi-periodic oscillations (kHz QPOs) at ~ 690 Hz from the transient neutron star low-mass X-ray binary EXO 1745-248. We find that this is a lower kHz QPO, and systematically study the time…

We analyze the time variability of the X-ray emission of RE J1034+396, an active galactic nucleus with the first firm detection of a quasi-periodic oscillations (QPO). Based on the results of a wavelet analysis, we find a drift in the QPO…

Using data obtained with the Rossi X-ray Timing Explorer, we report the detection of a 5 Hz quasi-periodic oscillation (QPO) in the bright low-mass X-ray binary and Z source Cygnus X-2 during high overall intensities (the high intensity…

The Neutron Star X-ray binary Sco X-1 is one of the brightest Z-type sources in our Galaxy, showing frequent periods of flaring activity and different types of relativistic outflows. Observations with RXTE have shown that the strongest…

The X-ray quasi-periodic oscillation (QPO) is a remarkable form of variability in systems of compact object accretion. RE J1034+396, harboring the most significant X-ray QPO in active galactic nuclei (AGNs), is the most noteworthy source…

We report on an RXTE/PCA observation of Aql X-1 during its outburst in March 1997 in which, immediately following a Type-I burst, the broad-band 2-10 keV flux decreased by about 10% and the kilohertz QPO frequency decreased from 813+-3 Hz…

In a recent outburst which lasted for 260 days, the black hole candidate GRO J1655-40 exhibited a behaviour similar to its last outburst observed almost eight years ago. We analyze a total of 150 observational spells in 122 days of data…

We studied the low-frequency quasi-periodic oscillations (LFQPOs) in the black hole GRO J1655-40 during the 2005 outburst, using data from the Rossi X-ray Timing Explorer. All LFQPOs could be identified as either type B or type C using…

Kilohertz quasi-periodic oscillations (kHz QPOs) are believed to originate from the orbital timescales of the inner accretion flow, reflecting the dynamics of the innermost disk regions under strong gravitational forces. Despite numerous…

We study the correlations between timing and X-ray spectral properties in the low mass X-ray binary 4U 0614+09 using a large (265-ks) data set obtained with the Rossi X-ray Timing Explorer. We find strong quasi-periodic oscillations (QPOs)…

Low and intermediate frequency quasi-periodic oscillations (QPOs) in black hole candidates are believed to be due to oscillations of the Comptonizing regions in an accretion flow. Assuming that the general structure of an accretion disk is…

We detected millihertz quasi-periodic oscillations (QPOs) in an XMM-Newton observation of the neutron-star low-mass X-ray binary 4U 1636-53. These QPOs have been interpreted as marginally-stable burning on the neutron-star surface. At the…

We investigate spectro-temporal properties for two black hole X-ray binary sources, MAXI J1535$-$571 and H 1743$-$322, during their hard and hard-intermediate states. For MAXI J1535$-$571, we analyze Swift/XRT, NuSTAR and NICER…

We report the timing results with Insight-HXMT observations of X-ray binary IGR J19294+1816 during its 2019 Type I outburst at the decline phase shortly following its peak. We analyze the light curves and power density spectrum (PDS) of the…

The transient Galactic black hole candidate Swift\,J1727.8-1613 went through an outburst for the very first time in August 2023 and lasted for almost 6 months. We study the timing and spectral properties of this source using publicly…

In recent observations with the Rossi X-Ray Timing Explorer we have detected two simultaneous quasi-periodic oscillation (QPO) peaks in the low mass X-ray binary and atoll source 4U 1735-44. The lower and higher frequency QPOs have…

Quasi-periodic oscillations (QPOs) are observed in the hard state of many black hole X-ray binaries. Although their origin is unknown, they are strongly associated with the corona, of which the geometry is also subject to discussion. We…

We report on the detection of optical/near-infrared (O-IR) quasi-periodic oscillations (QPOs) from the black hole X-ray transient Swift J1727.8-1613. We obtained three X-ray and O-IR high-time-resolution observations of the source during…