Related papers: Links Between Z Sources and Atoll Sources
We analysed 14 observations with kilohertz quasi-periodic oscillations (kHz QPOs) of the neutron star X-ray binary XTE J1701$-$462, the first source to show a clear transition between atoll and Z-like behaviour during a single outburst. We…
We have analyzed 866 RXTE observations of the 2006-2007 outburst of the accreting neutron star XTE J1701-462, during which the source evolves from super-Eddington luminosities to quiescence. The X-ray color evolution first resembles the Cyg…
We study the spin evolution of X-ray neutron stars in binary systems, which are being spun up by mass transfer from accretion disks. Our investigation reveals that a quark phase transition resulting from the changing central density induced…
(Abridged) We report on ten weeks of RXTE observations of the X-ray transient XTE J1701-462. Comparisons with other sources suggest it had all the characteristics of the neutron star Z sources (the brightest persistent neutron star LMXBs).…
AIMS: For six neutron-star atoll sources (4U 1608-52, 4U 1636-53, 4U 0614+09, 4U 1728-34, 4U 1820-30 and 4U 1735-44) we investigate the relationship between the observed fractional rms amplitudes of the twin kHz QPOs. We discuss whether…
Pairs of quasi-periodic oscillations (QPOs) at kilohertz frequencies are a common phenomenon in several neutron-star low-mass X-ray binaries. The frequency separation of the QPO peaks in the pair appears to be constant in many sources and…
Z-sources are a particular class of neutron star low-mass X-ray binaries characterized by a wide Z-like track in their hard colorsoft color (or hardness-intensity) diagrams, with three branches: the horizontal (HB), the normal (NB), and the…
We report the discovery of millihertz quasi-periodic oscillations (mHz QPOs) from the bursting, high-inclination atoll neutron-star low-mass X-ray binary (NS LMXB) EXO 0748--676 with the Rossi X-ray Time Explorer (RXTE). This class of QPO,…
Galactic accretion driven stellar X-ray sources can be divided into groups in different ways. An important division, which covers almost all known X-ray binaries, can be made according to the mass of the donor star: high-mass X-ray binaries…
Starting from the observation that kilohertz Quasi Period Oscillations (kHz QPO) occur in a very narrow range of X-ray luminosities in neutron star low mass X-ray binaries, we try to link the kHz QPO observability to variations of the…
A simple, physically consistent model has been proposed that seeks to explain in a unified way the X-ray spectra and rapid X-ray variability of the so-called Z sources and other accreting neutron stars in low-mass systems. Here we summarize…
The neutron stars in low-mass X-ray binaries (LMXBs) are usually thought to be weakly magnetized objects accreting matter from their low-mass companions in the form of a disk. Albeit weak as compared to those in young neutron-star systems,…
We study the formation of low-mass X-ray binaries (LMXBs) through helium star supernovae in binary systems that have each emerged from a common-envelope phase. LMXB progenitors must satisfy a large number of evolutionary and structural…
We review and discuss recent results on the search for correlations between astrophysical neutrinos and gamma-ray-detected sources, with many extra-galactic studies reporting potential associations with different types of blazars. We…
Burst-only sources are X-ray sources showing up only during short bursts but with no persistent emission (at least with the monitoring instrument which led to their discovery). These bursts have spectral characteristics consistent with…
We have studied the rapid X-ray time variability in 99 pointed observations with the Rossi X-ray Timing Explorer (RXTE)'s Proportional Counter Array of the low-mass X-ray binary 1E~1724--3045 which includes, for the first time, observations…
Ultra-luminous X-ray sources (ULXs) are those X-ray sources located away from the centre of their host galaxy with luminosities exceeding the Eddington limit of a stellar-mass black hole ($L_X>10^{39}\;{\rm erg\,s}^{-1}$). The discovery of…
Low-mass X-ray binaries (LMXBs) have been studied in the Galaxy since the beginning of X-ray astronomy. A lot has been learned about these bright X-ray sources, but significant questions are still open. These questions are related to the…
We present new results based on observations carried out with the Rossi X-ray Timing Explorer during the decay of an outburst of the low-mass X-ray binary (LMXB) and atoll source 4U 1608-52. Our results appear to resolve, at least in 4U…
We analyzed all published frequencies, nu_1 and nu_2, of the twin kilohertz quasi-periodic oscillations (kHz QPOs) in bright neutron star low-mass X-ray binaries. The two frequencies are well correlated but, contrary to recent suggestions,…