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On the origin of the difference between the runaway velocities of the OB-supergiant X-ray binaries and the Be/X-ray binaries
The recent finding by Chevalier & Ilovaisky (1998) from Hipparcosobservations that OB-supergiant X-ray binaries have relatively largerunaway velocities (mean peculiar tangential velocity avvt = 42 +/- 14\kms), whereas Be/X-ray binaries have low runaway velocities (avvt = 15+/- 6 \kms), provides confirmation of the current models for theformation of these two types of systems. These predict a difference inrunaway velocity of this order of magnitude. This difference basicallyresults from the variation of the fractional helium core mass as afunction of stellar mass, in combination with the conservation oforbital angular momentum during the mass transfer phase that precededthe formation of the compact object in the system. This combinationresults into: (i) Systematically narrower pre-supernova orbits in theOB-supergiant systems than in the Be-systems, and (ii) A largerfractional amount of mass ejected in the supernovae in high-mass systemsrelative to systems of lower mass. Regardless of possible kickvelocities imparted to neutron stars at birth, this combination leads toa considerable difference in average runaway velocity between these twogroups. If one includes the possibility for non-conservative masstransfer the predicted difference between the runaway velocity of thetwo groups becomes even more pronounced. The observed low runawayvelocities of the Be/X-ray binaries confirm that in most cases not morethan 1 to 2 \msun\ was ejected in the supernovae that produced theirneutron stars. This, in combinatioThe values given here are not identical (though similar) to those listedin Chevalier & Ilovaisky (1998). The corrections we applied areoutlined below.
| The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
| U, V, W velocity components for the old disk using radial velocities of 1295 stars in the three cardinal Galactic directions
New radial velocities are presented for 1295 stars chosen at random nearthe three cardinal Galactic directions of l = 180 deg, b = 0; l = 90deg, b = 0 deg; and b = 90 deg, giving the distribution in U, V, and W,respectively, from the radial velocities alone. The measurements weremade with the coude spectrograph of the Mount Wilson 100 in. Hookerreflector. The purpose of the program is to set limits on the densitynormalization in the solar neighborhood of the old thin disk, the oldthick disk, and the halo. Many more high-velocity stars are present inthe unbiased sample than expected from previous estimates of thenormalization. The data suggest the density ratios in the solarneighborhood to be about 90 percent, 10 percent, and about 0.5 percentfor the thin disk, thick disk, and halo populations, respectively.
| Micrometric Measures of Double Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974ApJS...28..413V&db_key=AST
| Mesures d'étoiles doubles faites au réfracteur de 38 cm de l'Observatoire de Nice
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