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Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
| ICCD speckle observations of binary stars. VIII - Measurements during 1989-1991 from the Cerro Tololo 4 M telescope
One-thousand eighty-eight observations of 947 binary star systems,observed by means of speckle interferometry with the 4 m telescope onCerro Tololo, are presented. These measurements, made during the period1989-1991, comprise the second installment of results stemming from theexpansion of our speckle program to the southern hemisphere.
| A survey of chromospherically active stars
Photometric and/or spectroscopic observations have been obtained of 52late-type stars which are suspected or known to be chromosphericallyactive. Although not all types of observations were obtained for eachstar, these observations include all-sky BVRI Johnson photometry,ultraviolet spectrograms, low-dispersion blue-wavelength spectrograms,and high-dispersion red-wavelength spectrograms. From the spectroscopicobservations v sin i's, radial velocities, and the appearance of the CaII H and K emission lines have been determined as well as the H-alphaline. The photometric observations indicate that chromosphericallyactive stars have V - R and V - I color excesses. Such excesses willaffect the surface fluxes determined with the surface brightness-colorrelationship. On the other hand all-sky BVRI photometry appears to be anexcellent way to identify chromospherically active stars. A small groupof moderately rapidly rotating, possibly single G8-K2 giants has beenfound. These stars have very modest chromospheric activity and so arenot FK comae stars. A number of other unusual chromospherically activestars are identified.
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