High-mass X-ray Binary System Research Articles

Optical and near-infrared observations of the microquasar V4641 Sgr during the 1999 September outburst

We present photometric and spectroscopic optical and near-infrared (NIR) observations taken during the outburst of the microquasar V4641 Sgr = SAX J1819.3 - 2525 in 1999 September. We observed an increase in the J - K s colour between 5 and 8 d after the outburst, which we interpret as likely evidence for the presence of dust around the source. We also observed an extraordinarily strong, broad and variable Ha line, with a velocity width of 4560 km s - 1 , suggesting the presence of a high-velocity outflow component. We constrain the distance of the system between 3 and 8 kpc, locating it further away than previously derived from radio observations, but consistent with results from Orosz et al. We then discuss the nature of this system, showing that the companion star is either a B3-A2 main-sequence star or a B3-A2 subgiant crossing the Hertzsprung gap. The system is therefore an intermediate- or high-mass X-ray binary system (IMXB or HMXB). The distance derived by these optical/NIR observations implies that the jets observed by Hjellming et al. would then exhibit apparent velocities of ∼10c. We finally discuss the possibility of an interaction between the jets and surroundings of the source, and also of this source being a 'microblazar'.

Hot plasma and black hole binaries in starburst galaxy M82.

High-resolution x-ray observations of the prototype starburst galaxy Messier 82 (M82) obtained with the advanced CCD (charge-coupled device) imaging spectrometer on board the Chandra X-ray Observatory provide a detailed view of hot plasma and energetic processes. Plasma with temperature of about 40,000,000 kelvin fills the inner 1 kiloparsec, which is much hotter than the 1,000,000 to 2,000,000 kelvin interstellar medium component in the Milky Way Galaxy. Produced by many supernova explosions, this central region is overpressurized and drives M82's prominent galactic wind into the intergalactic medium. We also resolved about 20 compact x-ray sources, many of which could be high-mass x-ray binary star systems containing black holes.

RXTEObservations of the X‐Ray Binary 2S 0114+650

Observations from the proportional counter array experiment on board the Rossi X-Ray Timing Explorer (RXTE) of the temporal and spectral properties of the high-mass X-ray binary 2S 0114+650 are reported. We find highly variable X-ray emission modulated at a period of 2.73 hr. The temporal results indicate that 2S 0114+650 is the slowest neutron star rotator presently known. Spectral analysis reveals parameters typical of a high-mass X-ray binary system having an absorbed power law with an index of about 1.3 with a high-energy cutoff at approximately 8 keV. The introduction of a fluorescent iron line at 6.4 keV allowed better spectral fits, particularly during low states of emission. We have also determined that the intensity of 2S 0114+650 is strongly attenuated during part of the orbit, which makes it a member of the small class of eclipsing massive X-ray binaries.

On the formation of wind bow-shocks around OB runaway stars

The interaction of the stellar wind of a supersonically moving massive star with its surrounding interstellar medium can result in the formation of an observable bow-shock. Recent studies at optical and infrared wavelengths indicate the presence of wind bow-shocks around several OB runaways, including the high-mass X-ray binary system Vela X-1. A large fraction of runaway stars do not seem to form wind bow-shocks. Obviously, when the local sound speed is high (∼ 100 km s−1), as is the case e.g., inside a hot superbubble, the (subsonic) space velocity would not be sufficient to form a bow-shock. Two-dimensional time-dependent hydrodynamical simulations indicate that the bow-shock is generally unstable; for certain combinations of ISM and wind parameters a bow-shock is not formed at all. The runaway nature of Wolf-Rayet stars in relation to the formation of wind bow-shocks is also discussed.

Tidal mass transfer in elliptical-orbit binary stars

High mass X-ray binary star systems with elliptical orbits, like GX 301-2, often exhibit a peak in X-ray luminosity associated with periastron passage. We use a two dimensional hydrodynamics code to examine the possibility that these X-ray flares result from tidal stripping of gas from the primary star, and subsequent accretion of this gas onto the compact companion. We find that if the primary star is rotating near corotation with the orbiting compact companion at periastron, tidally stripped gas can accrete, causing X-ray flares. Such a tidally induced flare will occur substantially after periastron, at a phase of ∼ 0.2 for the parameters used in our model. This flare is characterized by a brief disk accretion phase with a large angular momentum accretion rate. However, in our particular model this disk accretion phase was followed by an equally brief phase of accretion with the opposite sign of angular momentum, resulting in no long-term spin up of the X-ray pulsar.

A population synthesis study of high-mass X-ray binaries

The formation of high-mass X-ray binary systems is followed using a statistical Monte Carlo approach. The evolution of an initial distribution of binary systems is followed through mass transfer and mass loss or common envelope evolution to the supernova phase. The population synthesis is explored as a function of the form and magnitude of the kick velocity associated with asymmetric supernova explosions, the specific angular momentum of the matter lost from the system, the mass ratio above which the system enters into the common envelope phase, and the common envelope efficiency. To account for the observed systems with B-type companions in the orbital period–eccentricity plane, the results of the study strongly suggest that asymmetric explosions are required. Furthermore, the existence of systems with Be-type companions, in conjunction with the above, indicates that the specific angular momentum of matter lost (relative to that of the binary) during the mass transfer/loss phase is high (∼5).

Magnetic and spin evolution of pulsars

We explore the consequences of the model of spin-down-induced flux expulsion for the magnetic field evolution in solitary as well as in binary neutron stars. The spin evolution of pulsars, allowing for their field evolution according to this model, is shown to be consistent with the existing observational constraints in both low- and high-mass X-ray binary systems. The contribution from pulsars recycled in massive binaries to the observed excess in the number of low-field (10(11)-10(12) G) solitary pulsars is argued to be negligible in comparison with that of normal pulsars undergoing a 'restricted' field decay predicted by the adopted field decay model. Magnetic fields of neutron stars born in close binaries with intermediate- or high-mass main-sequence companions are predicted to decay down to values as low as similar to 10(6) G, which would leave them unobservable as pulsars during most of their lifetimes. The post-recycling evolution of some of these systems can, however, account for the observed binary pulsars having neutron star or massive white dwarf companions. Pulsars recycled in the disc population low-mass binaries are expected to have residual fields greater than or similar to 10(8) G, while for those processed in globular clusters larger residual fields are predicted because of the lower field strength of the neutron star at the epoch of binary formation. A value of tau similar to 1-2 x 10(7) yr for the mean value of the Ohmic decay time-scale in the crusts of neutron stars is suggested, based on the consistency of the model predictions with the observed distribution of periods and magnetic fields in the single and binary pulsars.

Wind dynamics in SMC X-1. 1: Hydrodynamic simulation

We present a three-dimensional hydrodynamic simulation of the disrupted stellar wind in the high-mass X-ray binary system SMC X-1. The three dominant processes that determine the geometry of the wind in high X-ray luminosity systems such as SMC X-1 are the X-ray suppression of the stellar wind from the X-ray irradiated face of the primary star, the focusing of the radiatively driven wind in the X-ray shadow by the effects of stellar rotation, and the rapid X-ray heating of gas in the vicinity of the X-ray source, including the X-ray illuminated surface of the primary star. The resulting distribution of circumstellar gas provides a successful explanation for the asymmetric, extended eclipse transitions and the intensity of the deep eclipse X-ray emission in SMC X-1, as well as a possible explanation for the X-ray dips seen near superior conjunction of the X-ray source in Cyg X-1.

The shadow wind in high-mass X-ray binaries

We present hydrodynamic simulations of the most X-ray luminous high-mass X-ray binary systems, such as Cen X-3 and SMC X-1. These models illustrate the presence of both a normal radiatively driven wind confined to the X-ray shadow of the primary star -- a shadow wind -- and a thermally driven wind excited by the X-ray heating of the primary's stellar surface -- an X-ray-excited wind. The X-ray flux in these systems is sufficiently intense that any circumstellar gas exposed to the X-ray source will be highly photoionized. These extreme ionization conditions prevent the formation of a normal radiatively driven wind from the irradiated surface of the primary, but such a wind can still form on the shadowed side of the primary. Orbital rotation can then bring this shadow wind into the line of sight toward the X-ray source, enhancing the column density of the wind seen near eclipse egress. Furthermore, such a high X-ray flux can also excite a thermal wind from the irradiated surface of the primary. Again, orbital rotation tends to deflect the wind, this time leading to an enhanced column density near eclipse ingress.

The Einstein Galactic plane survey. II - Optical observations of Northern Hemisphere X-ray sources

view Abstract Citations (25) References (40) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Einstein Galactic Plane Survey. II. Optical Observations of Northern Hemisphere X-Ray Sources Hertz, Paul ; Grindlay, Jonathan E. Abstract A statistically complete sample of x-ray sources observable from the northern hemisphere has been chosen from the Einstein Galactic Plane Survey, a flux- limited x-ray survey of the Galactic plane. The subset of the Galactic Plane Survey containing this northern sample covered 185 sq. deg of the Galactic plane with a median-limiting flux of 0.032 IPC counts s^-1^ (~7.4 X 10^-13^ erg cm^-2^ s^-1^). The northern sample contains 67 x-ray sources. A program of photometric and spectroscopic observations has been undertaken, and optical identifications are proposed for 45 (~67%) of the sources. Most of the unidentified sources must be noncoronal in nature, and statistical arguments imply that the majority of the unidentified sources are extragalactic. There is no evidence for a large class of low-luminosity Galactic accretion sources in the northern sample, and we place constraints on the spatial density of any such class. We present the results of our observing program, including finding charts of the unidentified x-ray sources. We note that the x-ray source 1E 1926.0 + 1927 is identified with the Wolf-Rayet star Roberts 93 and has an anomolously high x-ray-to-optical flux ratio for a Wolf-Rayet star. We suggest that this source may be a high-mass x-ray binary system containing a neutron star accreting stellar-wind-fed material from the Wolf-Rayet star. Publication: The Astronomical Journal Pub Date: July 1988 DOI: 10.1086/114805 Bibcode: 1988AJ.....96..233H Keywords: Northern Hemisphere; Sky Surveys (Astronomy); Wolf-Rayet Stars; X Ray Sources; Active Galactic Nuclei; Neutron Stars; Statistical Analysis; Astronomy; ULTRAVIOLET: GENERAL; X-RAYS: SOURCES full text sources ADS | data products SIMBAD (67) NED (16)