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The region of Collinder 121
The distribution of bright B-type stars in a field with a radius of5° centred at the Galactic open cluster Cr 121 is studied utilizingStrömgren and Hβ photometry. All PPM stars earlier thanspectral type A0 are used, revealing a loose nearby structure at adistance of 660-730pc, and a compact more distant group, which appearsto be a genuine cluster: Cr 121. Based on similar coordinates, distancesand positions on the colour-magnitude (CM) and Hertzsprung-Russell (HR)diagrams, 11 photometric cluster members are selected at a mean distanceof 1085(+/-41 standard error) pc. The results are discussed in the lightof both classical and Hipparcos points of view.
| Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Secondary standard stars for UVBY beta CCD photometry
Accurate standard uvby indices are presented for 73 southern B, A, F andG stars in the $V$ magnitude range 8.2 to 10.9. They cover all threetransformation regions of the $uvby$ system (Olsen \cite[1983]{Olsen1})well. Standard $\beta$ indices are included for the 55 B, A, and F starsin the sample. Our results provide a useful set of secondary standardsfor uvby beta CCD photometry with southern hemisphere 1-2 m classtelescopes. A critical comparison with published photometry, in generalbased on fewer observations, is given. Based on observations made at theEuropean Southern Observatory, La Silla, Chile. Tables 3, 4, 5 are alsoavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Uvby-beta observations of 528 type B stars with V between the 8th and 9th magnitude
The paper presents uvby-beta measurements of 528 type B stars selectedfrom the SAO Catalog on the basis of two criteria: the spectral types inthe range B3-B5 and mV between the 8th and the 9th magnitude. Reddeningindependent (c1) values are estimated from the spectral classificationand compared to the observed values. No systematic trend with observed(b-y), H-beta, or spectral type appears to be present, but the range of(c1) residuals is surprisingly large. A rather large part of the starshas small beta values, smaller than for the BIa supergiants. Only twoare classified as O stars and most of them have the suffix e, ne, ornne. Most beta values for the O type stars are slightly above the upperlimit of 2.585 m.
| 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.
| Broad-band photometry of selected southern ultraviolet-bright stars.
Not Available
| The evolution of low ionization QSO absorption systems
A CCD spectroscopic survey of Mg II and Mg I absorption lines in a C IVselected sample of 35 metal systems, observed toward 12 QSOs between z =1.1 and z = 2.1, is reported. Six Mg I and 10 Mg II absorption lines aredetected in 33 C IV clouds, and some peculiarities are noted. Thecomplex or asymmetric line profiles reveal that multiple components arepresent and that variations in the C IV/Mg II and Mg II/Mg I ratio mayoccur often from one component to another with a velocity separationless than the velocity resolution of about 100 km/s. Comparison with theMg II absorption-line statistics at z-bar = 0.5 implies that, at z-bar =1.6, there are more strong absorbers per unit z with W(2796) greaterthan 0.6 A and fewer weak absorbers. The evolutionary parameter gammaappears to depend on W(min): its value drops as W(min) is reduced and isnegative at W(min) = 0.15 A. This suggests a different redshiftevolution for the population of weak and strong Mg II absorbers.
| The ultraviolet spectrum and interstellar environment of HD 50896
Data from 92 high-resolution IUE 1150-3274-A spectra are compiled intables and graphs and analyzed in detail to characterize HD 50896 andits interstellar environment. Findings reported include unexceptionaldepletions in the low-velocity H I system, strong low-velocity lines(attributed to excitation in an H II region associated with HD 50896 atdistance 2-3 kpc), an absorption system blueshifted by about 30 km/sfrom the low-velocity gas (attributed to ring nebula S308), andhigh-velocity absorption systems with evidence of grain destruction(attributed to an old SNR).
| High-velocity interstellar gas in the line of sight to the Wolf-Rayet star HD 50896
The large shell of interstellar gas (IG) discovered toward HD 50896 byHeckathorn and Fesen (1984) is characterized on the basis ofhigh-dispersion IUE SWP and LWR spectra of 19 objects located within 4deg of HD 50896 (but outside the optical ring nebula S308) at distances0.6-2.9 kpc (compared to 1.5 kpc for HD 50896). The IG is found to havetwo components (at velocities -80 and -125 km/s), diameter 90 pc orgreater, and distance 1.0 + or - 0.2 kpc, demonstrating that it is notrelated to HD 50896 and suggesting that it is a highly evolved supernovaremnant associated with cluster Cr 121.
| Optical observations of ultraviolet objects. I - Spectral classification of 103 stars /l = 200-275 deg/
Results are presented of a program of spectral classification of 103stars originally selected as ultraviolet objects from TD-1 satellitephotometry with the S2/68 experiment. Most of the objects appear to bespectroscopically normal stars; the method of selection yielded a sampleof relatively unreddened B stars at distances up to about 2 kpc. Thisresult is compared with recent studies of the spatial distribution ofinterstellar extinction in the same regions of the sky.
| The region of NGC 2287 and CR 121
Intermediate band and H-beta observations of 135 stars in the regions ofthe clusters NGC 2287 and Cr 121 are discussed, and a luminositycalibration of photometric parameters for late G- to early K-type brightgiants and supergiants is introduced. Results indicate that NGC 2287 isat a distance of 740 pc, very little reddened, 100-million years old,and contains three or four G8-K2 bright giants and supergiants and ablue straggler. Cr 121 is 1.17 kpc distant, very little reddened, 1.5million years old and an extension of CMa OB1. Cr 121 contains a nearerconcentration of stars at the same distance as NGC 2287, and theassociation appears to be the same age as CMa OB1, although presequencestars may exist. Intermingling of stars in CMa OB2 and NGC 2287 is alsoconsidered possible, and a test of the calibration of two methods ofluminosity determination of early A-type stars using photometricparameters shows them to be entirely consistent.
| H-beta photometry of southern early-type stars
H-beta photoelectric photometry is presented for 209 southern hemisphereearly-type stars from the HD catalog with galactic latitudes /b/ greaterthan 6 deg. Four-color photometry exists for all these stars and MKtypes for most of them. Absolute magnitudes have been estimated for allbut the emission-line stars and distances from the sun and the galacticplane determined.
| Four colour photometry of southern early-type stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978MNRAS.182..629K&db_key=AST
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | כלב גדול |
| התרוממות ימנית: | 06h50m58.09s |
| סירוב: | -24°23'53.8" |
| גודל גלוי: | 8.946 |
| מרחק: | 1265.823 פארסק |
| תנועה נכונה: | -3.7 |
| תנועה נכונה: | 5.5 |
| B-T magnitude: | 8.74 |
| V-T magnitude: | 8.929 |
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