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A study of interstellar Nai D absorption lines towards the Lupus molecular clouds
Intermediate-resolution (60000<=R<=120000) observations ofinterstellar Nai lines towards 29 stars in the general direction of theLupus molecular clouds (330°<~l<~350°0°<~b<~25°) are presented. Previously published spectratowards an additional seven stars are also included. Based on theHipparcos distances to these stars, and the minimum distance at whichstrong interstellar Nai lines appear in the spectra, I obtain a distanceof ~150+/-10pc to the Lupus molecular complex. While in agreement with anumber of other independent estimates, this result is at odds with thevalue of 100pc recently obtained by Knude & Høg from aHipparcos-based study of interstellar extinction. A possible explanationfor this discrepancy is discussed, and it is concluded that the value of150+/-10pc obtained here is to be preferred. In addition, theseobservations have some other implications for the structure of theinterstellar medium in this direction, and these are briefly considered.
| 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.
| Physical parameters of stars in the Scorpio-Centaurus OB association
Walraven photometry is presented of established and probable members ofthe Scorpio-Centaurus OB association. For each star, effectivetemperature and surface gravity are derived using Kurucz (1979)atmosphere models. From the Straizys and Kuriliene (1981) tables,absolute magnitudes are calculated. Distance moduli and visualextinctions are determined for all stars. From a comparison of theHR-diagrams of the stars in each subgroup with theoretical isochrones,the ages of the three subgroups are derived. The distances to the threesubgroups are shown to be different; there is a general trend (alsowithin each subgroup) for the distances to be larger at higher galacticlongitudes. The visual extinction in the youngest subgroupUpper-Scorpius, is well correlated with the IRAS 100-micron map. Thedistance toward the Ophiuchus dark clouds is found to be 125 pc, basedon the photometric distances to the stars. Most of the early-type starsin Upper-Scorpius are located at the far side of the dark clouds.
| UVBY and beta observations of B-type stars in the Scorpio-Centaurus association.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971AJ.....76.1041G&db_key=AST
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