We present a catalogue of low-mass X-ray binaries. The catalogue is an updated version of the catalogue of van Paradijs (1995). This new catalogue contains 150 sources, 31 new low-mass X-ray binaries in addition to the 119 sources listed in van Paradijs' catalogue. The aim of this catalogue is to help the reader gain easy access to the recent literature (up to about August 2000) on individual sources, and to provide of some basic information on the X-ray sources and their counterparts in other wavelength ranges (UV, optical, IR, and radio). In cases where there is some doubt about the low-mass nature of the X-ray binary, this is mentioned. In an appendix we list the Anomalous X-ray Pulsars (AXPs), which nowadays are no longer thought to be low-mass X-ray binaries.

/pdf/a-catalogue-of-low-mass-x-ray-binaries-tb6g9n68ps.pdf

A catalogue of low-mass X-ray binaries

We present the first detection of the mass donor star in the prototype X-ray binary Scorpius X-1 Phase-resolved spectroscopy revealed narrow emission line components from the irradiated secondary star Radial velocity fits to the Bowen blend emission are used to establish an absolute orbital ephemeris and derive an accurate value for the systemic velocity, γ = -1138 ± 06 km s-1 Emission from the irradiated front side of the secondary leads to solid limits to the radial velocity of the mass donor of 87 K2 148 km s-1 In conjunction with an upper limit to the velocity of the primary K1 ≤ 53 km s-1, we derive a firm limit on the mass ratio of Sco X-1 of q 061 A likely set of system parameters satisfying the various constraints as well as the recent inclination estimate by Fomalont, Geldzahler, & Bradshaw (2001) is K1 = 40 km s-1, K2 = 133 km s-1, q = 030 corresponding to component masses of M1 = 14 M☉ and M2 = 042 M☉ for an orbital inclination of 38°

pdf/the-mass-donor-of-scorpius-x-1-revealed-1xj8ngchxz.pdf

The Mass Donor of Scorpius X-1 Revealed

We present NuSTAR observations of Vela X-1, a persistent, yet highly variable, neutron star high-mass X-ray binary (HMXB). Two observations were taken at similar orbital phases but separated by nearly a year. They show very different 3–79 keV flux levels as well as strong variability during each observation, covering almost one order of magnitude in flux. These observations allow, for the first time ever, investigations on kilo-second time-scales of how the centroid energies of cyclotron resonant scattering features (CRSFs) depend on flux for a persistent HMXB. We find that the line energy of the harmonic CRSF is correlated with flux, as expected in the sub-critical accretion regime. We argue that Vela X-1 has a very narrow accretion column with a radius of around 0.4 km that sustains a Coulomb interaction dominated shock at the observed luminosities of L_x ~ 3 × 10^36 erg s^−1. Besides the prominent harmonic line at 55 keV the fundamental line around 25 keV is clearly detected. We find that the strengths of the two CRSFs are anti-correlated, which we explain by photon spawning. This anti-correlation is a possible explanation for the debate about the existence of the fundamental line. The ratio of the line energies is variable with time and deviates significantly from 2.0, also a possible consequence of photon spawning, which changes the shape of the line. During the second observation, Vela X-1 showed a short off-state in which the power-law softened and a cut-off was no longer measurable. It is likely that the source switched to a different accretion regime at these low mass accretion rates, explaining the drastic change in spectral shape.

/pdf/nustar-discovery-of-a-luminosity-dependent-cyclotron-line-5eua1tizjf.pdf

NuSTAR Discovery of a Luminosity Dependent Cyclotron Line Energy in Vela X-1

Optical spectra of the black hole candidate X-ray binary LMC X-l reveal that the system is surrounded by an extended, highly ionized He III region, N159F, which appears to be the long-sought-for example of an X-ray-photoionized nebula The spatially resolved temperature and ionization structure allows us to measure the previously unobservable extreme ultraviolet (EUV) luminosity of an accreting compact object

Detection of an X-ray-ionized nebula around the black hole candidate binary LMC X-l

Classical Supergiant X-ray Binaries (SGXBs) and Supergiant Fast X-ray Transients (SFXTs) are two types of High-mass X-ray Binaries (HMXBs) that present similar donors but, at the same time, show very different behavior in the X-rays. The reason for this dichotomy of wind-fed HMXBs is still a matter of debate. Among the several explanations that have been proposed, some of them invoke specific stellar wind properties of the donor stars. Only dedicated empiric analysis of the donors' stellar wind can provide the required information to accomplish an adequate test of these theories. However, such analyses are scarce. To close this gap, we perform a comparative analysis of the optical companion in two important systems: IGR J17544-2619 (SFXT) and Vela X-1 (SGXB). We analyse the spectra of each star in detail and derive their stellar and wind properties. We compare the wind parameters, giving us an excellent chance of recognizing key differences between donor winds in SFXTs and SGXBs. We find that the stellar parameters derived from the analysis generally agree well with the spectral types of the two donors: O9I (IGR J17544-2619) and B0.5Iae (Vela X-1). An important difference between the stellar winds of the two stars is their terminal velocities v_inf=1500km/s in IGR J17544-2619 and v_inf=700km/s in Vela~X-1, which has important consequences on the X-ray luminosity of these sources. Their specific combination of wind speed and pulsar spin favours an accretion regime with a persistently high luminosity in Vela X-1, while it favours an inhibiting accretion mechanism in IGR~J17544-2619. Our study demonstrates that the wind relative velocity is critical in the determination of the class of HMXBs hosting a supergiant donor, given that it may shift the accretion mechanism from direct accretion to propeller regimes when combined with other parameters.

/pdf/measuring-the-stellar-wind-parameters-in-igr-j17544-2619-and-3qq308l6eh.pdf

Measuring the stellar wind parameters in IGR J17544-2619 and Vela X-1 constrains the accretion physics in Supergiant Fast X-ray Transient and classical Supergiant X-ray Binaries

Ultraviolet, visible, infrared, and X-ray observations of Scorpius X-1

UV spectra (obtained by the IUE) of HD 77581, associated with the binary X-ray source Vela X-1, show a spectrum typical of an early B-type supergiant. However, the P Cygni profiles of strong resonance lines show substantial variations with orbital phase. These variations can be ascribed to the changing ionization state in the stellar wind caused by the X-ray emitting companion. X-ray and spectroscopic and photometric optical observations, simultaneous with the IUE observations, indicate behavior consistent with previous epochs.

Simultaneous ultraviolet, optical, and X-ray observations of the X-ray source Vela X-1 /HD 77581/

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Ultraviolet, visible, infrared, and X-ray observations of Scorpius X-1

Simultaneous ultraviolet, optical, and X-ray observations of the X-ray source Vela X-1 /HD 77581/