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CCD photometry and astrometry for visual double and multiple stars of the HIPPARCOS catalogue III. CCD photometry and differential astrometry for 253 southern ``intermediate'' systems
We present new astrometric and photometric data for 253 visual doublestars of the ``intermediate'' class, i.e. with angular separations inthe range 1 to 15 arcsec. The multi-colour observations were obtained in1992-94 as part of the ESO Key Programme ``Visual Double Stars''performed at La Silla Observatory (Chile). Differential magnitudes andcolours have been secured in a systematic way while component magnitudesand colour indices have been determined in the V and I passbands of theCousins standard system in good photometric conditions only. Internaland mean external errors are smaller than respectively 0.01 mag and afew hundreths of a magnitude (typically less than 0.03 mag). Relativepositions are obtained as a by-product with internal errors of the orderof 0.006 arcsec in angular separation (corresponding to pixel width x0.02) and 0.07 degr in position angle. Final accuracies are thoroughlydiscussed: we illustrate the overall excellent quality of the data andestimate the quality degradation for angular separations barely largerthan the width of the seeing disk. Based on observations made at LaSilla (ESO, Chile, Key Programme 7-009-49K).
| The distance to the nearest star-forming clouds: MBM12 and MBM20
We present high-resolution spectra (R ~ 49,000) of stars that haveparallax measurements from the Hipparcos satellite and are projectedalong the line of sight to the two nearest known star forming clouds tothe Sun: MBM12 and MBM20. The spectra were obtained with the FOCESEchelle Spectrograph at the 2.2 meter telescope in Calar Alto, Spain andthe wavelength range was chosen to include the interstellar Na I D linesat lambda 5889.950 Ä and lambda 5895.924 Ä. Since the starsare at a range of distances, we use their spectra along with theirparallaxes from Hipparcos to determine the distance to the moleculargas. The stars in front of the cloud do not show interstellar Na I Dabsorption features while the stars behind the cloud do showinterstellar absorption features. We find that both clouds are somewhatmore distant than previously estimated. The revised distance to MBM12 is58+/-5 pc < d < 90+/-12 pc and the distance to MBM20 is 112+/-15pc < d < 161+/-21 pc.
| Photometric and spectroscopic analysis of high galactic latitude molecular clouds. II - High-resolution spectroscopic observations of NA I, CA II, CA I, CH, and CH(+1)
High-resolution spectroscopic observations in the wavelengths of thespecies Na I, Ca II, and Ca I and the molecular species CH and CH(+)have been performed toward stars behind a variety of high galacticlatitude molecular clouds (HLCs). Seventeen new detections of molecularabsorption are reported. The sizes, densities, and molecular contentfound for the HLCs are consistent with an interpretation of HLCmolecular cores as extremely compact structures of enhanced molecularcontent which may have evolved from larger H I shells.
| Photometric and spectroscopic analysis of high Galactic latitude molecular clouds. I - Distances and extinctions of stars toward 25 selected regions
The paper presents new photoelectric photometry in the UBV, uvby, andH-beta systems for 320 stars at high Galactic latitudes, selected fortheir proximity to the densest portions of a variety of high Galacticlatitude atomic and molecular clouds. Low-resolution digital spectra areemployed to classify 115 of the stars. Several novel techniques aredeveloped for automatic digital spectral classification, and fordereddening Stromgren uvby-beta and Johnson UBV,H-beta photometry. Anempirical determination of the errors in the derived dereddened colors,and techniques for converting between the two photometric systems arepresented on the basis of the analysis of a statistically significantsample of 1480 stars with complete data sets in both photometric systemsand with an accurate MK spectral type. New constraints on the distancesto several clouds are presented.
| Stromgren and H-beta photometry of stars earlier than G0 in 5 areas containing high latitude molecular clouds
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1989A&AS...80..127F&db_key=AST
| Visual multiples. VIII - 1000 MK types
A total of 1000 new classifications are given for stars brighter than B= 8.0 mag in the Aitken double star catalog. The classificationssupplement 865 classifications obtained in 1981 and 1984. Among thenewly discovered stars are 12 new Ap stars, eight Lambda Bootis stars,one Ba II star, and 60 Am stars. A detailed list of the newclassifications is given.
| A Note about the Comparison Between the Old and New Slettebak Systems of Axial Rotational Velocities
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1984RMxAA...9....9G&db_key=AST
| Rotational velocities and spectral types for a sample of binary systems.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975A&AS...19...91L&db_key=AST
| Photovisual differences in magnitudes of 331 mainly southern double stars
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