CN column densities and excitation temperatures
We analyse abundances and rotational temperatures of the interstellar CNmolecule. We have calculated the column densities and excitationtemperatures of the molecule along 73 lines of sight basing on ouroriginal measurements of the B 2?+ -X2?+ (0,0) vibrational band recorded in highsignal-to-noise ratio spectra and also for 88 directions based onmeasurements already available in literature. We compare the columndensities obtained from different bands of CN molecule available toground-based instruments. The obtained excitation temperatures in theanalysed directions show always an excess over the cosmic microwavebackground radiation (CMBR) temperature.
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A Preliminary Investigation of the Diffuse Interstellar Line at 8621 Å
We have obtained high-resolution spectra at the Dominion AstrophysicalObservatory, the Calar Alto Observatory, and the European SouthernObservatory of hot stars in the near-infrared region to study thediffuse interstellar band (DIB) at 8621 Å. Field stars as well asselected members of the Perseus spiral arm, the ρ Ophiuchi complex,and the Cygnus OB2 association were observed and the equivalent widthsof the band measured, as well as interstellar K I absorption at 7699Å. In total we measure the equivalent width of the 8621 band in 64stars. In a series of figures we show the correlations of the DIB withreddening, polarization, K I, and strengths of other DIBs at 5780, 5797,and 6613 Å. The quality of the correlations are discussed by meansof the Spearman rank correlation test. Good correlations are found withreddening and, among the other DIBs, 8621 correlates best with 5780. Byexamining the three special regions mentioned above we confirm theweakness of the 8621 DIB in the hot stars of the ρ Oph star-formingregion. In the Perseus spiral arm region we find that the DIBs areformed largely in foreground clouds but not in the gas that appears tohave been blown away from the young massive stars of the Perseus arm. InCyg OB2 we find that the equivalent widths of the 8621 line lie abovethe linear correlation of equivalent width with E(B-V) and theirstrength does not vary as strongly with reddening. The heavily reddenedCyg OB2 star 12 is the most extreme example of the relativeinsensitivity of the 8621 equivalent width to reddening in the CygnusOB2 region.
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Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
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New Estimates of the Solar-Neighborhood Massive Star Birthrate and the Galactic Supernova Rate
The birthrate of stars of masses >=10 Msolar is estimatedfrom a sample of just over 400 O3-B2 dwarfs within 1.5 kpc of the Sunand the result extrapolated to estimate the Galactic supernova ratecontributed by such stars. The solar-neighborhood Galactic-plane massivestar birthrate is estimated at ~176 stars kpc-3Myr-1. On the basis of a model in which the Galactic stellardensity distribution comprises a ``disk+central hole'' like that of thedust infrared emission (as proposed by Drimmel and Spergel), theGalactic supernova rate is estimated at probably not less than ~1 normore than ~2 per century and the number of O3-B2 dwarfs within the solarcircle at ~200,000.
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Catalog of Galactic OB Stars
An all-sky catalog of Galactic OB stars has been created by extendingthe Case-Hamburg Galactic plane luminous-stars surveys to include 5500additional objects drawn from the literature. This work brings the totalnumber of known or reasonably suspected OB stars to over 16,000.Companion databases of UBVβ photometry and MK classifications forthese objects include nearly 30,000 and 20,000 entries, respectively.
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Interstellar CN toward CH+-forming regions
Measurements on interstellar CN absorption are presented for stars inthree southern OB associations, NGC 2439, Vela OB1, and Cen OB1. CN isdetected in 21 out of 31 stars observed. The doublet ratio for the R(1)and P(1) lines of the (0, 0) band of the B 2Sigma+-X 2Sigma + violet system and acomparison of violet system data with measurements of the (1, 0) and (2,0) bands of the A 2Pi -X 2Sigma + redsystem are used to derive Doppler parameters and total column densities.Inferred CN column densities vary by more than an order of magnitude forlines of sight with similar CH column densities. Observations of the (0,0) band of the CH B 2Sigma --X 2Pisystem are used to revise previously published CH column densitiestoward the lines of sight studied in CN. Together with earlier resultson CH, CH+, and C2, the CN data presented hereprovide a homogeneous set of column densities and radial velocities ofdiatomic molecules in three individual translucent clouds. We use thesedata to study CN production via chemical models. Gas densities areinferred from models based on production via CH and C2 incool gas. Most sightlines in our sample test densities typical fordiffuse molecular gas (a few hundred cm-3 ) when theultraviolet flux permeating the gas is between 1 and 5 times the averageinterstellar flux. A few lines of sight indicate that CN is producedunder dark cloud conditions because relatively large densities areobtained or because this simple chemical scheme is unable to reproducethe observed CN columns. Low densities are indicated for directions withupper limits on CN. We add an ad hoc component of a number oflow-velocity (<10 km s-1) criss-crossing MHD shocks toexplain observed column densities of interstellar CH+. Theseshocks also produce about 10 to 30% of the total CH column along theline of sight.
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H I Shells behind the Coalsack
We report the discovery of two new large H I shells in the direction ofthe Coalsack Nebula. Both shells were observed with the Parkes RadioTelescope as part of the Southern Galactic Plane Survey. The largestshell, GSH 304-00-12, is at a distance of ~1.2 kpc and has derivedphysical dimensions of 280×200 pc. The second shell, GSH305+01-24, is at a distance of ~2.2 kpc and has derived dimensions of280×440 pc. We present a simple numerical model to show that GSH305+01-24 most likely formed from stellar winds in the Centaurus OB1stellar association. There is associated radio, infrared, and Hαcontinuum emission. Both shells are situated in the Sagittarius-Carinaarm, with GSH 305+01-24 more distant. The far edge of GSH 304-00-12 isat the near side of the arm and opens into the interarm region. We findno evidence of closure at the near side of the shell and thereforedescribe the geometry as conical. Emission from the near side of theshell may be lost in absorption by the Coalsack Nebula.
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Interstellar C_2 absorption lines towards CH+ forming regions
Interstellar C_2 absorption line observations towards the southern OBassociations NGC 2439, Vela OB1, and Cen OB1 are used to infergaskinetic temperatures Tkin and densities nctowards lines of sight with previously determined large CH andCH+ column densities. Towards NGC 2439, the material ischaracterised by temperatures of Tkin = 75-85 K and densitiesexceeding nc > 1000 C_2m, and a fractional C_2 abundanceof about x(C_2) = 1.5 10-8. Temperatures and densitiesinferred towards two stars in Vela OB1 are Tkin = 65-85 K andnc >= 600 C_2m. C_2 fractional abundances in the cloudcomplex obscuring Vela OB1 are about half the value found in NGC 2439.For the lines of sight towards Cen OB1, values of Tkin =70-95 K and fractional abundances of x(C_2) ~ 5 10-9 arefound, and towards HD 114213, Tkin = 25 K and nc =400+/-100 C_2m. The observations demonstrate that C_2 resides in coolgas at temperature of Tkin < 100 K. The C_2 columndensities are correlated with those of CH, which is expected fromtheoretical models. This suggests that CH is efficiently formed in thecool material as well, together with C_2. This finding does not supportexpectations from recent MHD and vortex models of CH+formation, which stipulate that neutrals such as CH are abundantlyproduced in hot regions of many 100 K temperature.
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Five-colour photometry of OB-stars in the Southern Hemisphere
Observations of OB-stars, made in 1959 and 1960 at the Leiden SouthernStation near Hartebeespoortdam, South Africa, with the VBLUW photometerattached to the 90 cm light-collector, are given in this paper. They arecompared with photometry obtained by \cite[Graham (1968),]{gra68}\cite[Walraven & Walraven (1977),]{wal77} \cite[Lub & Pel(1977)]{lub77} and \cite[Van Genderen et al. (1984).]{gen84} Formulaefor the transformation of the present observations to those of\cite[Walraven & Walraven (1977)]{wal77} and \cite[Lub & Pel(1977)]{lub77} are given. Table 4 is only available in electronic format the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/Abstract.html
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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.
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Red and infrared colours of B stars and the reddening law in the Galaxy
The red and infrared intrinsic colours of B stars are derived fromphotometric observations through the UBV(RI)_CJHK and Hβ filters of257 early-type stars. Those stars for which the UBV and Hβmeasurements match the published spectral class, and which show no othersigns of peculiarity, are used to determine the intrinsic photometriccolours of B stars in the red and infrared. From these intrinsic coloursthe interstellar reddening relationships for the red and infraredcolours are evaluated, and the results are compared with previousestimates of these quantities. The values of R, E(B-V) and the distanceare then determined for the individual stars. R is confirmed to be closeto 3.1 in most cases, but was found to be much larger in somedirections. The relationship between R and the location of a star in theGalaxy is investigated. Usually the abnormally reddened stars seemed tobe associated with known regions of star formation. The paper alsoidentifies seven likely variable stars and a number of stars withpossible dust shells.
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Interstellar CH^+^ in southern OB associations.
Optical absorption line observations of interstellar CH^+^ and CH arepresented towards the southern OB associations CMa OB1, NGC 2439, VelaOB1, NGC 4755, and Cen OB1. A total of 5-11 stars per association wereobserved, with visual extinctions ranging from A_V_=0.5-4.5mag. Thederived CH^+^ and CH velocities agree within the measurement errors.Towards a particular association, the CH^+^ column density N(CH^+^) iscorrelated to the visual extinction of the background star. Thesefindings weaken the possibility that magnetic shocks are the generalmechanism that is required to produce interstellar CH^+^. It is foundthat N(CH^+^) is correlated to N(CH), which indicates that N(CH^+^) iscorrelated to the optical depth of a cloud. The correlations aredifficult to reconcile with scenarios where the sites of CH^+^ formationare constrained to the surface of molecular clouds. The observationssupport ideas which involve turbulence as a major CH^+^ productionmechanism. In particular, the results are in agreement with expectationsfrom a scenario where the CH^+^ formation proceeds in cool gas via afraction of fast, non-Maxwellian H_2_ or C^+^, created by thedissipation of interstellar turbulence.
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A Radial Velocity Database for Stephenson-Sanduleak Southern Luminous Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....113..823R&db_key=AST
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Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
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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.
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Stromgren and H-Beta Photometry of Associations and Open Clusters - Part Three - CENTAURUS-OB1 and CRUX-OB1
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994MNRAS.269..289K&db_key=AST
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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.
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Photometric Two-Dimensional Classification of Stars and Interstellar Extinction in the Coalsack Area - Part One
Not Available
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Interstellar C2, CH, and CN in translucent molecular clouds
Optical absorption-line techniques have been applied to the study of anumber of translucent molecular clouds in which the total columndensities are large enough that substantial molecular abundances can bemaintained. Results are presented for a survey of absorption lines ofinterstellar C2, CH, and CN. Detections of CN through the A 2Pi-X2Sigma(+) (1,O) and (2,O) bands of the red system are reported andcompared with observations of the violet system for one line of sight.The population distributions in C2 provide diagnostic information ontemperature and density. The measured column densities of the threespecies can be used to test details of the theory of molecule formationin clouds where photoprocesses still play a significant role. The C2 andCH column densities are strongly correlated with each other and probablyalso with the H2 column density. In contrast, the CN column densitiesare found to vary greatly from cloud to cloud. The observations arediscussed with reference to detailed theoretical models.
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UBV-beta photometry of luminous early-type stars and emission-line stars in the Southern Coalsack region
A catalog is presented giving UBV-beta photometry for 144 luminous OBstars and UBV photometry for 154 emission-line stars in a 100-sq-degregion around the Southern Coalsack. Total visual absorptions anddistance moduli have been determined for all the stars and aretabulated. Comparisons with previous observations are discussed.
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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.
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Spectroscopic binary frequency among CNO stars
Radial velocities of 35 stars with carbon, nitrogen, and oxygen (CNO)anomalies in the OB spectral range have been measured. Using these newdata, it has been confirmed that the short-period spectroscopic binaryfrequency among the OBN stars is substantially larger than among the OBCstars. After allowance for the undiscovered systems, practically allstars with nitrogen anomalies belong to short-period spectroscopicbinaries, while the frequency among the OBC stars is statisticallysimilar to the frequency of normal supergiants. Among the stars withmoderate nitrogen anomalies, a frequency of short-period binaries whichranges between 50 percent (N-enhanced) and 83 percent (N-deficient) wasfound.
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On the intrinsic UVBY colours of early-type supergiants
The present photoelectric uvby observations of 43 late O-type to earlyA-type supergiants are combined with published results to extend theZhang (1983) determination of the intrinsic color lines in the(b-y)/c(1) diagram. Zhang's conclusion that the H-beta index is wellcorrelated with luminosity class is reaffirmed by the results obtained,although the degree of separation found here is less clear. It is notfound, however, that beta has a significant minimum between the B1 andB3 spectral types.
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The evolutionary status of OB stars with peculiar nitrogen spectra
The majority (60 percent) of OB stars exhibiting nitrogen abundancepeculiarities are members of stellar associations. The rate ofmembership is typical of O and WR stars. Bolometric magnitudes for the46 known associated peculiar OB stars (25 overabundant and 21 deficient)demonstrated that most of the anomalous stars are the brightest in theassociations. Grouping the anomalous stars in an aggregate age-classwith the next-brightest stars in the associations and then examining thecluster age reveals that nitrogen-rich OB stars are found in young andold clusters and nitrogen-poor objects are in intermediate ageassociations. Further details show that 30 solar mass OB have a nitrogenenrichment in the main sequence. Old clusters with nitrogen-rich OBstars can contain blue stragglers, which are also nitrogen-enriched.Some of the nitrogen-enriched stars are WNE progenitors or are a branchof a late evolutionary phase. Finally, nitrogen-rich OB stars areusually hotter than nitrogen-poor OB stars.
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A study of B-type supergiants with the uvby,beta photometric system
The applicability of the uvby,beta photometric system to theclassification and study of B-type supergiants (BTS) is investigatedusing published data on 157 BTS and observations of 17 BTS made with the36-in. reflector at McDonald Observatory. The results are presented intabular form and analyzed to produce preliminary calibrations ofluminosity class vs. beta index and of absolute magnitude (Mv) vs. beta(or delta Mv vs. delta beta) for four associations of stars. Theeffectiveness of various color indices as temperature indicators isdiscussed. It is shown that there is good correspondence between MK anduvby,beta classifications of B-type main-sequence stars, giants, andBTS, confirming the usefulness of the uvby,beta system in furtherresearch on BTS.
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UBV photometry for southern OB stars
New UBV photometry of 1227 OB stars in the southern Milky Way ispresented. For 1113 of these stars, MK spectral types have been reportedpreviously in a comprehensive survey to B = 10.0 mag.
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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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The interstellar extinction law in some dusty HII regions
UBVRI data for 62 O and B stars in dusty H II regions and for nine fieldstars are presented. The data are used to investigate the reddening lawin the range BVRI. For the field stars and the H II regions M8, M20, S5,S66, S67, the normal interstellar extinction law has been confirmed.However, in NGC 6334, NGC 6357 and M16 unusually high color excessratios have been found: E(V-R)/E(B-V) and E(V-I)/E(B-V), indicatingabnormal values of the ratio of total to selective extinction, R equals3.8 for NGC 6334/6357 and R equals 4.0 for M16.
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Infrared photometry of southern early-type stars
The paper presents infrared photometry tied to the JHKL (1.2-3.5microns) broadband photometric system for 229 southern early-type stars.To determine data for stars of low reddening intrinsic visual-IR colorindices were used; the E(V-K)/E(B-V) diagram was applied to evaluate theratio of total selective extinction. A mean value of R = 3.12 plus orminus 0.05 was found for stars close to the galactic plane, but a highervalue of R (about 4.0) applies to the Orion and Sco-Oph regions.Infrared two-color diagrams were used to investigate the occurrence ofinfrared excess emission in different classes of shell star; no excesseswere found for supergiants or Of stars. It is concluded that theanomalous position HD 164740 in the two-color diagrams is produced bystrong infrared excess and not by a peculiar extinction law.
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Studies of luminous stars in nearby galaxies. I. Supergiants and O stars in the Milky Way.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978ApJS...38..309H&db_key=AST
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INHABITED SKY
