Proper-motion binaries in the Hipparcos catalogue: comparison with radial velocity data

Context. This paper is the last in a series devoted to the analysis of the binary content of the Hipparcos Catalogue. Aims. The comparison of the proper motions constructed from positions spanning a short (Hipparcos) or long time (Tycho-2) makes it possible to uncover binaries with periods of the order of or somewhat larger than the short time span (in this case, the 3 yr duration of the Hipparcos mission), since the unrecognised orbital motion will then add to the proper motion. Methods. A list of candidate proper motion binaries is constructed from a carefully designed χ2 test evaluating the statistical significance of the difference between the Tycho-2 and Hipparcos proper motions for 103 134 stars in common between the two catalogues (excluding components of visual systems). Since similar lists of proper-motion binaries have already been constructed, the present paper focuses on the evaluation of the detection efficiency of proper-motion binaries, using different kinds of control data (mostly radial velocities). The detection rate for entries from the Ninth Catalogue of Spectroscopic Binary Orbits (SB9) is evaluated, as well as for stars like barium stars, which are known to be all binaries, and finally for spectroscopic binaries identified from radial velocity data in the Geneva-Copenhagen survey of F and G dwarfs in the solar neighbourhood. Results. Proper motion binaries are efficiently detected for systems with parallaxes in excess of ∼20 mas, and periods in the range 1000-30 000 d. The shortest periods in this range (1000-2000 d, i.e. once to twice the duration of the Hipparcos mission) may appear only as DMSA/G binaries (accelerated proper motion in the Hipparcos Double and Multiple System Annex). Proper motion binaries detected among SB9 systems having periods shorter than about 400 d hint at triple systems, the proper-motion binary involving a component with a longer orbital period. A list of 19 candidate triple systems is provided. Binaries suspected of having low-mass (brown-dwarf-like) companions are listed as well. Among the 37 barium stars with parallaxes larger than 5 mas, only 7 exhibit no evidence for duplicity whatsoever (be it spectroscopic or astrometric). Finally, the fraction of proper-motion binaries shows no significant variation among the various (regular) spectral classes, when due account is taken for the detection biases. © ESO 2007.

The diencephalic syndrome in infants: A review in relation to optic nerve glioma

A study of the diencephalic syndrome in cases so far collected from the literature was carried out on the clinical, macroscopic and histological brain findings found recorded in, respectively, 29, 25 and 34 cases. For comparison, 3 further cases with this syn- drome were described, in which a diagnosis of optic nerve glioma could be made. The review of the 39 cases with the diencephalic syndrome has shown that in 90°/o of these patients an extensive glioma of the 3rd ventricle had been present. 70% of these patients had additional glioma of optic nerves and/or chiasm with an equal amount of infants having diminished visual acuity in one or both eyes. From these, so far unreported, findings, strong suggestive evidence was thus presented that the ‘diencephalic syndrome’ described in infants was indeed a mor¬bid entity, namely, a hypothalamo-optic glioma. The further question whether this brain tumour was a primary optic nerve rather than a primary diencephalic glioma could presently not be firmly answered from the reviewed data of the literature. © 1972 S. Karger AG, Basel.

410 - Phase transitions induced by coloured voltage noise in nerve membranes

Quantitative conditions are derived under which electrically excitable membranes can undergo a phase transition induced by an externally applied voltage noise. The results obtained for a non-cooperative and a cooperative form of the two-state model are compared. © 1981.