Related papers: NGC 300 ULX1: spin evolution, super-Eddington accr…
Thanks to long-term X-ray monitoring, a number of interacting binaries are now known to show X-ray periodicities on timescales of tens to hundreds of binary orbits. In some systems, precession of a warped accretion disc is the leading model…
We report the first detection of flux variability in the most luminous X-ray source in the southern ring of the Cartwheel galaxy. XMM--Newton data show that the luminosity has varied over a timescale of six months from L[0.5-10] keV \~1.3…
Using BATSE and RXTE observations from 1991 April to 2001 August we have detected 71 outbursts from 82 periastron passages of EXO 2030+375, a 42-second transient X-ray pulsar with a Be star companion, including several outbursts from 1993…
We report a systematic analysis of the spin, orbital, and superorbital modulations of 4U 0114+650, a high-mass X-ray binary consists of one of the slowest spinning neutron stars. Utilizing the dynamic power spectrum, we found that the spin…
A scenario of the formation of isolated X-ray pulsars is discussed with an application to one of the best studied objects of this class 1E 161348-5055. This moderately luminous, 10^33 - 10^35 erg/s, pulsar with a relatively soft spectrum,…
Ultraluminous X-ray sources (ULXs) are a population of extragalactic objects whose luminosity exceeds the Eddington limit for a 10 Msun black hole (BH). Their properties have been widely interpreted in terms of accreting stellar-mass or…
Ultraluminous X-ray sources (ULXs) are non-nuclear point-like objects observed with extremely high X-ray luminosity that exceeds the Eddington limit of a $\rm10\,M_\odot$ black hole. A fraction of ULXs has been confirmed to contain neutron…
Using X-ray data from the Rossi X-Ray Timing Explorer (RXTE), we report the pulse timing results of the accretion powered high mass X-ray binary (HMXRB) pulsar 4U 1907+09 covering a time span of almost two years. We measured three new pulse…
Ultraluminous X-ray Sources (ULXs) provide a unique opportunities to probe the geometry and energetics of super-Eddington accretion. The radiative processes involved in super-Eddington accretion are not well understood, and so studying…
We report the analysis of the first superburst from a transiently accreting neutron star system with the All-Sky Monitor (ASM) on the Rossi X-ray Timing Explorer. The superburst occurred 55 days after the onset of an accretion outburst in…
We present our Swift monitoring campaign of the slowly rotating neutron star Be/X-ray transient GX 304-1 (spin period of ~275 s) when the source was not in outburst. We found that between its type-I outbursts the source recurrently exhibits…
We report the results of a 2019-2021 monitoring campaign with Swift and associated target-of-opportunity observations with XMM-Newton and NuSTAR, examining the spectral and timing behavior of the highly variable ultraluminous X-ray source…
GRS 1915+105 is a transient black hole X-ray binary consistently emitting 10-100% of the Eddington luminosity in the X-ray band during the last three decades until mid-2018 when the source luminosity suddenly decreased by an order of…
On 2016 July 30 (MJD 57599), observations of the Small Magellanic Cloud by Swift/XRT found an increase in X-ray counts coming from a position consistent with the Be/X-ray binary pulsar SMC X-3. Follow-up observations on 2016 August 3 (MJD…
We review observations of ultraluminous X-ray sources (ULXs). X-ray spectroscopic and timing studies of ULXs suggest a new accretion state distinct from those seen in Galactic stellar-mass black hole binaries. The detection of coherent…
Majority of ultraluminous X-ray sources (ULXs) are believed to be super-Eddington objects, providing a nearby prototype for studying an accretion in super-critical regime. In this work, we present the study of time-lag spectra of the ULX…
During the summer of 2006, the accreting X-ray pulsar EXO 2030+375 underwent its first giant outburst since its discovery in 1985. Our observations include the first ever of the rise of a giant outburst of EXO 2030+375. EXO 2030+375 was…
Rotation-powered millisecond radio pulsars have been spun up to their present spin period by a $10^8$ - $10^9$ yr long X-ray-bright phase of accretion of matter and angular momentum in a low-to-intermediate mass binary system. Recently, the…
A sub-set of the brightest ultraluminous X-ray sources (ULXs), with X-ray luminosities well above $10^{40}$ erg s$^{-1}$, typically have energy spectra which can be well described as hard power-laws, and short-term variability in excess of…
We describe observations of the 2003 outburst of the hard-spectrum X-ray transient 4U 1901+03 with the Rossi X-ray Timing Explorer. The outburst was first detected in 2003 February by the All-Sky Monitor, and reached a peak 2.5-25 keV flux…