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CCD astrometry and UBV photometry of visual binaries. II. Visual double stars with mainly G - type primaries and relatively small angular separation
Differences Delta V of magnitude and Delta (B-V) and Delta (U-B)colours, as well as separations and position angles of 42 relativelyclose double stars are presented. The selection criteria of our sampleare: the relatively small separation (between 2.5 and 5 arcseconds),magnitude difference under 1.25 mag, and mainly G-type primaries. TheCCD observations, performed at the 90 cm Dutch telescope at ESO, weremade using the Bessel U, B and V filters; the astrometry was done in theV filter only. From the analysis of the photometric data we concludethat 16 binaries in our sample have components with practically the sameT_eff, since they have almost the same colours; one binary hascomponents with identical characteristics. We also note the goodinternal accuracy of the astrometric CCD measurements. Based onobservations made at ESO La Silla, Chile.
| Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
| Synchronization in early-type spectroscopic binary stars
The rotational properties of a large sample of noneclipsing double-linedspectroscopic binaries are discussed in terms of synchronization ofaxial and orbital rotation. The data covered the spectral types OB andA04, i.e., those with full radiative envelopes. Nearly 80 systems wereinvestigated, and the periods and orbital velocities are provided. Ahigh correlation was found between the fractional radius and theoccurrence of synchronicity and pseudosynchronicity. Deviations fromsynchronous rotation were most apparent at fractional radii of 0.05 andbelow. Current theories of the synchronization time scales are noted tobe inadequate for describing the small fractional radii-lack ofsynchronism observed.
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