Related papers: Pulse Frequency Fluctuations of Persistent Accreti…
Context: Monitoring of pulse period variations in accreting binary pulsars is an important tool to study the interaction between the magnetosphere of the neutron star and the accretion disk. While the X-ray flux of the brightest X-ray…
We have investigated properties of the Quasi Periodic Oscillation (QPO) features in the accretion powered X-ray pulsar Cen X-3 over a period of about four years using observations carried out with the Proportional Counter Array (PCA) of the…
Because of its complex clumpy wind, prominent cyclotron resonant scattering features, intrinsic variability and convenient physical parameters (close distance, high inclination, small orbital separation) which facilitate the observation and…
We present observational evidence for "propeller" effects in two X-ray pulsars, GX 1+4 and GROJ1744-28. Both sources were monitored regularly by the Rossi X-ray Timing Explorer (RXTE) throughout a decaying period in the X-ray brightness.…
We investigate timing and spectral characteristics of the transient X-ray pulsar 2S 1417$-$624 during its 2018 outburst with \emph{NICER} follow up observations. We describe the spectra with high-energy cut-off and partial covering fraction…
We have investigated the stability of the pulse frequency second derivatives ($\ddot \nu $) of PSR 0823+26, PSR 1706-16, PSR 1749-28, PSR 2021+51 which show significant quadratic trends in their pulse frequency histories in order to…
We report the discovery of kHz fluctuations, including quasi-periodic oscillations (QPO) at ~330 Hz and ~760 Hz and a broadband kHz continuum in the power density spectrum of the high mass X-ray binary pulsar Centaurus X-3. These…
Context: In addition to coherent pulsation, many accreting neutron stars exhibit flaring activity and strong aperiodic variability on time scales comparable to or shorter than their pulsation period. Such a behavior shows that the accretion…
OAO 1657-415 is an eclipsing X-ray binary wind-fed pulsar that has exhibited smooth spin-up/spin-down episodes and has undergone several torque reversals throughout its long history of observation. We present a frequency history spanning…
We have monitored the pulse frequencies of the two soft gamma repeaters SGR 1806-20 and SGR 1900+14 through the beginning of year 2001 using primarily Rossi X-ray Timing Explorer Proportional Counter Array observations. In both sources, we…
We investigate aperiodic X-ray flux variability in accreting highly magnetized neutron stars - X-ray pulsars (XRPs). The X-ray variability is largely determined by mass accretion rate fluctuations at the NS surface, which replicate…
We analyzed the X-ray power density spectra of five ultraluminous X-ray sources (ULXs) NGC5408 X-1, NGC6946 X-1, M82 X-1, NGC1313 X-1 and IC342 X-1 that are the only ULXs which display both flat-topped noise (FTN) and quasi-periodic…
The operation of CGRO/BATSE continues to produce, after more than 5 years, a valuable database for the study of long-term variability in bright hard X-ray sources. The all-sky capability of BATSE provides, using the Earth occultation…
Long-term observations have shown that black hole X-ray binaries exhibit strong, aperiodic variability on time-scales of a few milliseconds to seconds. The observed light curves display various characteristic features like a log-normal…
We analysed an X-ray light curve of the dwarf nova RU Peg taken by XMM-Newton with a duration of 46300 s. The power density spectrum has a complicated shape with two red noise and two white noise components, indicating the presence of two…
We investigate the structure of the wind in the neutron star X-ray binary system Vela X-1 by analyzing its flaring behavior. Vela X-1 shows constant flaring, with some flares reaching fluxes of more than 3.0 Crab between 20-60 keV for…
We present a detailed pulse phase resolved spectral analysis of the persistent high mass X-ray binary pulsar Vela X-1 observed with Suzaku during June 2008. The pulse profiles exhibit both intensity and energy dependence with multiple peaks…
We report on long-term monitoring of anomalous X-ray pulsars (AXPs) using the Rossi X-ray Timing Explorer (RXTE). Using phase-coherent timing, we find a wide variety of behaviors among the sources, ranging from high stability (in 1E…
We analyzed the rapid aperiodic X-ray variability of the recently discovered millisecond X-ray pulsar SAX J1808.4-3658. The power density spectrum is dominated by a strong band-limited noise component, which follows a power-law with index…
We report on the RXTE/PCA observation of the X-ray burster 1E1724-3045 located in the globular cluster Terzan 2. The persistent X-ray emission shows a high level of noise variability, the so-called High Frequency Noise (HFN) with a…