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

After a long quiescence of three decades, the transient X-ray pulsar 4U 1901+03 became highly active in 2003 February. From the analysis of a large number of Rossi X-ray Timing Explorer/ Proportional Counter Array (RXTE/PCA) observations of…

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…

We have produced the colour-colour diagram of all the observations of 4U 1728-34 available in the Rossi X-ray Timing Explorer public archive (from 1996 to 2002) and found observations filling in a previously reported 'gap' between the…

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…

We report the discovery of kHz quasi periodic oscillations (QPOs) in three Rossi X-ray Timing Explorer observations of the low mass X-ray binary (LMXB) XTE J1701-407. In one of the observations we detect a kHz QPO with a characteristic…

We have discovered a 7.06+-0.08 Hz quasi-periodic oscillation (QPO) in the X-ray flux of the low-luminosity low-mass X-ray binary (LMXB) and atoll source 4U 1820-30. This QPO was only observable at the highest observed mass accretion rate,…

We report the discovery of a new class of low frequency quasi--periodic variations of the X-ray flux in the X-ray bursters 4U1608-52 and 4U1636-536. We also report an occasional detection of a similar QPO in Aql X-1. The QPOs, associated…

Quasi-periodic oscillations (QPOs) have been discovered in the X-ray emission of many neutron stars and black holes. The QPOs with frequencies greater than about 300 Hz are thought to be produced near the surfaces of neutron stars and the…

We report the results of a systematic timing analysis of RXTE observations of GRS 1915+105 when the source was in its variability class theta, characterized by alternating soft and hard states on a time scale of a few hundred seconds. The…

The Galactic transient black hole candidate (BHC) MAXI~J1834-021 was detected for the first time by MAXI/GSC on February 05, 2023 and it was active for next $\sim 10$~months. A monotonic evolution of low-frequency QPOs from higher to lower…

We report the discovery of 8.5 sigma high-frequency quasi-periodic oscillations (HFQPOs) at 66 Hz in the RXTE data of the black hole candidate IGR J17091-3624, a system whose X-ray properties are very similar to those of microquasar GRS…

Following the discovery of 3:2 resonance quasi-periodic oscillations (QPOs) in M82X-1 (Pasham et al. 2014), we have constructed power density spectra (PDS) of all 15 (sufficiently long) {\it XMM-Newton} observations of the ultraluminous…

Characterising the fast variability in black-hole low-mass X-ray binaries (BHXBs) can help us understand the geometrical and physical nature of the innermost regions of these sources. Particularly, type-B quasi-periodic oscillations (QPOs),…

We report the discovery of a 200mHz quasi-periodic oscillation (QPO) in the X-ray emission from a bright ultra-luminous X-ray source (ULX) Holmberg IX X-1 using a long XMM-Newton observation. The QPO has a centroid at…

Using archival data from the Rossi X-ray Timing Explorer (RXTE), we study in a systematic way the variation of the quality factor and amplitude of the lower and upper kHz quasi-periodic oscillations (QPO) in the low-mass X-ray binary…

We report the discovery of strong aperiodic X-ray variability and quasi-periodic oscillation (QPO) in the X-ray light curves of a new X-ray Nova, XTE J1550-564, and the evolution of the observed temporal properties during the rise of the…

Our goal is to investigate the X-ray timing and spectral variability of the high-mass X-ray binary 1A 1118-615 during a type-II outburst. We performed a detailed color, spectral and timing analysis of a giant outburst from 1A 1118-615,…

We report the discovery of a $\sim 1.5 \times 10^{-4}$ Hz ($\sim 2$ hr) X-ray quasi-periodic oscillation (QPO) in the active galaxy MS 2254.9-3712, using a $\sim 70$ ks XMM-Newton observation. The QPO is significantly detected ($\sim 3.3…

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…

We investigated the temporal behavior of the new black hole transient XTE J1650-500 with the Rossi X-ray Timing Explorer (RXTE) as the source made a transition to the low/hard state during the decay of the 2001 outburst. We find QPOs in the…