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Ice in the Southern Coalsack
To better understand the conditions under which ice mantles form ongrains in molecular clouds, three globules in the Southern Coalsack havebeen searched for the presence of H2 O ice. Given the totallack of star formation in the Coalsack, it is an ideal site for studyingunprocessed icy molecular mantles. In our sample of eight field starslying behind the Coalsack we detect strong H2 O iceabsorption in the lines of sight to two stars and possible weakabsorption in four others. We estimate H2 O ice columndensities or upper limits for these lines of sight. Compared to darkclouds such as Taurus, the Coalsack H2 O ice column densitiesare lower than expected given the quiescent nature of the Coalsackregion. It is possible that the chemical evolution of the Coalsack maysimply be at too early a stage for significant ice mantles to appear onthe grains, except perhaps in the densest parts of some of the globules.Alternatively, the presence or absence of ice absorption may be relatedto the distribution of dust along each line of sight, specifically, therelative contributions of dense globules and a more extended diffusecomponent. For example, our observations are consistent with an icethreshold extinction similar to that observed in the Taurus dark cloudif extinction amounting to A V ~5 towards Globules 2 and 3arises in the extended component. Globule 1 appears to have no extendedcomponent.
| UBV beta Database for Case-Hamburg Northern and Southern Luminous Stars
A database of photoelectric UBV beta photometry for stars listed in theCase-Hamburg northern and southern Milky Way luminous stars surveys hasbeen compiled from the original research literature. Consisting of over16,000 observations of some 7300 stars from over 500 sources, thisdatabase constitutes the most complete compilation of such photometryavailable for intrinsically luminous stars around the Galactic plane.Over 5000 stars listed in the Case-Hamburg surveys still lackfundamental photometric data.
| A spectroscopic database for Stephenson-Sanduleak Southern Luminous Stars
A database of published spectral classifications for objects in theStepenson-Sanduleak Luminous Stars in the Southern Milky Way catalog hasbeen compiled from the literature. A total of 6182 classifications for2562 stars from 139 sources are incorporated.
| Uvbyβ photometry of all stars earlier than G0 and brighter than m_pg_~10.3mag in Selected Area 194
Four-colour and Hβ photometry is introduced for 594 stars earlierthan G0 in the Kapteyn's Selected Area 194. The results give V, b-y,m_1_, c_1_, and β on the standard systems, with overall rms errorsfor one observation of one star of 0.009mag, 0.004mag, 0.006mag,0.009mag, and 0.009mag, respectively. The data cover an area of about5deg x 5deg and is intended for an investigation of the distribution ofthe interstellar medium toward the northern part of the SouthernCoalsack and its surroundings. A comparison to earlier results obtainedby other authors has shown that the c_1_ indices obtained for the latetype stars were underestimated, in average, by 0.020mag. Since suchdifference may account for an error of little more than 10% in theestimated stellar distances, a correction was applied to the c_1_ indexof these stars.
| The Fourier decomposition as a mode discriminator - New first overtone pulsators among Cepheids with P less than 5.5 D
New very accurate light curves of 12 Cepheids with P less than 5.5 d arepresented. Their Fourier decomposition enabled us to individuate eightother stars which do not follow the Hertzsprung progression. Theproperties of the Fourier parameters of this subclass, now composed by28 objects, are consequently better defined. In the phi(21)-P plane 2stars located on the lower sequence and 2 other stars located on thediscontinuity at 3 d were found. All these 28 stars occupy the sameregion in the R(21)-P plane and the phi(31) values, when available,originate a unique sequence in the phi(31)-P plane. All these loci arewell separated from those of the classical Cepheids, which arefundamental mode pulsators. The hypotheses of a first overtone pulsationand of a resonance between this mode and a higher overtone explain theobservational facts well.
| The calibration of the Stromgren photometric system for A, F and early G supergiants. I - The observational data
An empirical calibration of the Stromgren uvby-beta photometric systemfor the A, F, and early G supergiants is being derived. This paperexplains the observational program and the photometric reductiontechniques used and presents a catalog of new Stromgren photometry forover 600 A, F, and G supergiants.
| 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.
| Stromgren and H-beta photometry of stars earlier than G0 in the Southern Coalsack direction
Four-color and H-beta photometry have been obtained for 236 starsearlier than G0 in order to study the color excess distribution in theSouthern Coalsack direction. The beta histogram of the stars reveals arelative absence of stars in the range of A4 to A9. The (b-y)distribution for B-type stars suggests the existence of three differenttypes of stars located at different distances.
| Five-colour photometry of early-type stars in the direction of galactic X-ray sources
The results of five-color (Walraven system) photometry of 551 O- andB-type stars located in 17 fields of a few square degrees aroundgalactic X-ray sources are presented. From a comparison ofreddening-free combinations of color indices with theoretical values,calculated for model atmospheres of Kurucz (1979), effective temperatureand surface gravity for these stars are derived. In addition theirabsolute magnitude are determined by combining these parameters with theresults of evolutionary calculations of massive stars. These effectivetemperatures are in good agreement with the temperature scale ofBohm-Vitense (1981) for stars of luminosity classes II to V. For thesupergiants the effective temperatures are about 40 percent higher. Forstars of luminosity classes III to V the absolute magnitudes agree wellwith the results of independent luminosity calibrations of spectraltypes, but for brighter stars they deviate systematically. Thephotometric data are also used to study the interstellar reddening inthe direction of the X-ray sources.
| UBV photometry of the southern galactic cluster NGC 4755 = Kappa Crucis
UBV photoelectric magnitudes and colors are presented for 86 starstogether with photographic magnitudes and colors for 553 stars in thevicinity of the southern young open cluster NGC 4755. A true distancemodulus of 11.82 m is derived corresponding to a linear distance of 2.3kpc. The evolutionary age is determined to be between 8 and 11.5 x 10 tothe 6th years, depending on the assumed chemical composition of thecluster stars. The mean interstellar reddening E(B-V) across the clusterincreases with galactic latitude and angular distance from the Coalsackfrom about 0.40 m to 0.48 m with an average value of 0.44 m. The totalnumber of probable cluster members detected in the field down to alimiting visual magnitude of V = 16.0 m is 203. The linear gravitationalradius of the cluster obtained from star strip counts down to visualmagnitude 14.5 m is found to be 3.4 pc. The luminosity function derivedfor NGC 4755 is in good agreement with the initial luminosity functionas given by Sandage (1957). The cluster contains six supergiants andthree variable Be stars.
| Catalog of Luminous Stars in the Southern Coalsack Zone
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1982RMxAA...5..183M&db_key=AST
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Osservazione e dati astrometrici
| Costellazione: | Croce del Sud |
| Ascensione retta: | 12h50m12.00s |
| Declinazione: | -60°24'03.0" |
| Magnitudine apparente: | 6.75 |
| Distanza: | 729.927 parsec |
| Moto proprio RA: | -15.1 |
| Moto proprio Dec: | -4.3 |
| B-T magnitude: | 7.133 |
| V-T magnitude: | 6.775 |
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