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Abstract:

We have imaged the X-ray binary SS 433 with unprecedented Fourier plane coverage at 6 cm using simultaneously the Very Long Baseline Array (VLBA), MERLIN, and the Very Large Array and also at 20 cm using the VLBA. At both wavelengths we have securely detected smooth, low surface brightness emission having the appearance of a "ruff" or collar attached perpendicularly to the well-studied knotty jets in this system and extending over at least a few hundred AU. We interpret this smooth emission as a windlike outflow from the binary and discuss its implications for the present evolutionary stage of this system. © 2001. The American Astronomical Society. All rights reserved.

Abstract:

The most complete atlas of modern spectrophotometric observations of symbiotic stars is presented. It contains observations of 137 objects on both hemispheres. All spectra are absolutely calibrated in flux, they have un-saturated emission lines and generally a high signal/noise in the continuum. Opportunities for statistically relevant investigations of emission line spectrum and cool giant classification are briefly discussed. Distribution policy is mentioned.

Abstract:

The radio millisecond pulsar PSR B1620-26 is part of an extraordinary triple star system in the globular cluster M4. The inner companion to the neutron star is thought to be a white dwarf of mass m(1) similar or equal to 0.3 M-circle dot in an orbit of period similar or equal to 0.5 yr. The nature and orbital characteristics of the second, more distant companion, have remained a mystery for many years. A theoretical analysis of the latest available radio pulsar timing data is presented here, allowing us to determine approximately the mass and orbital parameters of the second companion. Remarkably, the current best-fit parameters correspond to a second companion of planetary mass, with m(2)sin i(2) similar or equal to 7 x 10(-3) M-circle dot, in an orbit of eccentricity e(2) similar or equal to 0.45 and with a large semimajor axis a(2) similar or equal to 60 AU. The short dynamical lifetime of this very wide triple in M4 suggests that large numbers of such planets must be present in globular clusters. We also address the question of the anomalously high eccentricity of the inner binary pulsar. While this eccentricity could have been induced during the same dynamical interaction that created the triple, we find that it could also naturally arise from long-term secular perturbation effects in the triple, combining the general relativistic precession of the inner orbit with the Newtonian gravitational perturbation by the outer planet.

Abstract:

Binary population synthesis (BPS) is an algorithm to evolve millions of stars (including binaries) simultaneously. It plays an important role in the theory of stellar evolution and is potentially important in the study of galaxies. Previous studies of BPS employed different assumptions in the explanations of different objects, and sometimes adopted non-physical model parameters. We try to establish a self-consistent BPS model in order to explain many objects in a self-consistent way and to avoid unnatural model parameters. We present the model and some preliminary results in this paper.

Abstract:

The outbursts of black hole X-ray transients can be understood as caused by a limit cycle instability in the accretion disk, similar to dwarf nova outbursts. For adequately low mass overflow rates from the companion star long outburst recurrence times are expected. But the fact that we find predominantly long recurrence times or that only one X-ray nova outburst was detected at all poses a problem. The question arises whether any braking mechanism could act in a way that long recurrence times are favoured.We suggest that a circumbinary disk exists and brakes the orbital motion of the binary stars by tidal interaction. The irradiation during an outburst leads to mass loss by winds from the circumbinary disk, relieving the braking force until the removed matter is refilled by diffusion from outer parts. We show that this reduction of braking will self-adjust the mass transfer to the marginal rate that gives long recurrence times.