High-Resolution Observations of Interstellar Ca I Absorption-Implications for Depletions and Electron Densities in Diffuse Clouds
We present high-resolution (FWHM~0.3-1.5 km s-1) spectra,obtained with the AAT UHRF, the McDonald Observatory 2.7 m coudéspectrograph, and/or the KPNO coudé feed, of interstellar Ca Iabsorption toward 30 Galactic stars. Comparisons of the column densitiesof Ca I, Ca II, K I, and other species-for individual componentsidentified in the line profiles and also when integrated over entirelines of sight-yield information on relative electron densities anddepletions (dependent on assumptions regarding the ionizationequilibrium). There is no obvious relationship between the ratio N(CaI)/N(Ca II) [equal to ne/(Γ/αr) forphotoionization equilibrium] and the fraction of hydrogen in molecularform f(H2) (often taken to be indicative of the local densitynH). For a smaller sample of sight lines for which thethermal pressure (nHT) and local density can be estimated viaanalysis of the C I fine-structure excitation, the average electrondensity inferred from C, Na, and K (assuming photoionizationequilibrium) seems to be independent of nH andnHT. While the electron density (ne) obtained fromthe ratio N(Ca I)/N(Ca II) is often significantly higher than the valuesderived from other elements, the patterns of relative nederived from different elements show both similarities and differencesfor different lines of sight-suggesting that additional processesbesides photoionization and radiative recombination commonly andsignificantly affect the ionization balance of heavy elements in diffuseinterstellar clouds. Such additional processes may also contribute tothe (apparently) larger than expected fractional ionizations(ne/nH) found for some lines of sight withindependent determinations of nH. In general, inclusion of``grain-assisted'' recombination does reduce the inferred ne,but it does not reconcile the ne estimated from differentelements; it may, however, suggest some dependence of ne onnH. The depletion of calcium may have a much weakerdependence on density than was suggested by earlier comparisons with CHand CN. Two appendices present similar high-resolution spectra of Fe Ifor a few stars and give a compilation of column density data for Ca I,Ca II, Fe I, and S I.
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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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The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
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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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Stromgren and Hβ photometry of OB stars in the region of the Carina Spiral Feature
Stromgren and Hβ photometry of 130 stars in the Carina section ofthe Milky Way is presented. The color excesses and the distances of allstars are obtained. A good agreement is found between the CM and HRdiagrams and the spatial distribution of these stars. Tables 1, 2, 4 and5 are only available in electronic form at the CDS via anonymous ftp to130.79.128.5 or via http://cdsweb.u-strasbg.fr/Abstract.html
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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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Interstellar Extinction from 0.35 to 2.2 Microns: A Study Based on Luminous Southern Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJS..101..335H&db_key=AST
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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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Millimetre observations of southern translucent clouds
Millimetre emission line observations of ^12^CO J=1-0 are presented fora sample of translucent molecular clouds previously studied by opticalabsorption lines towards background stars. The CO maps provideinformation on the extent, structure, mass and kinematics of theregions. In some clouds, the emission is characterized by a singlecomponent which does not vary much across the region. In other cases,multiple close-lying components or sheets are found, which may vary in aself-similar manner across the cloud. None of the clouds is close tosimple virial equilibrium. Sensitive searches for ^13^CO and C^18^OJ=1-0 emission have been made towards the stellar positions. C^18^O hasbeen detected in only 5 clouds, most of which have extinctions well inexcess of 2 mag. The inferred ^13^CO/C^18^O abundance ratios range from7-25, and the lower limits from >13 to >35. These values are asmuch as five times larger than the overall interstellar([^13^C].[^16^O])/([^12^C] .[^18^O]) ratio, suggesting thatisotope-selective photodissociation plays a role in at least some of theclouds. Searches for other molecules at millimetre wavelengths have beenmade for a few of the best characterized clouds. Surprisingly, noemission was detected from the C_2_H or C_3_H_2_ molecules, even thoughthe abundances of diatomic C_2_ and CH are quite large. On the otherhand, the abundance of HCO^+^ appears comparable to that found in denserclouds, and the abundance of HCN may be up to an order of magnitudelarger than the predictions of models in two clouds.
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Stromgren and H-Beta Photometry of OB Associations and Open Clusters - Part Two - TRIANGULUM:16 and CARINA:OB2
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993MNRAS.261..847K&db_key=AST
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The abundance of CH(+) in translucent molecular clouds - Further tests of shock models
Observations of interstellar absorption lines of CH(+) in the (0, 0) and(1, 0) bands of the A 1Pi - X 1Sigma(+) system are presented for 17stars with reddenings up to E(B-V) about 1.5 mag. Complementary data oninterstellar CH in the (0, 0) bands of the A 2Delta - X 2Pi and B2Sigma(-) - X 2Pi systems and C2 in the A 1Pi(u) - X 1Sigma(g)(+) redsystem have been obtained as well. The derived CH(+) column densitiescontinue to increase with total column density, and values up to 10 exp14/sq cm are reported for highly-reddened lines of sight. In most cases,the CH(+) and CH absorptions are dominated by a single strong component,with weaker features displaced by a few km/s. No significant velocitydifference is found between CH(+) and neutral species such as CH and CNfor this sample of randomly oriented lines of sight. In contrast withCN, the CH(+) abundance does not increase with the density in the cloudas derived from the observed C2 excitation. For the two clouds with thelargest density, HD 62542 and HD 94413, no CH(+) absorption is foundwith CH(+)/CH less than 0.03 and 0.14, respectively. The CH(+) findingsdo not support a single-shock origin for the formation of the ion.
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A study of reddened luminous stars in the southern Milky Way. IV. JHK photometry.
Not Available
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A study of reddened luminous stars in the southern Milky Way. III. VRI photometry.
Not Available
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A study of reddened luminous stars in the southern Milky Way. II. H-beta photometry, reddening and distances.
Not Available
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A study of reddened luminous stars in the southern Milky Way. UVBY photometry.
Not Available
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A multi-wavelength analysis of interstellar CN - Comparison of red and violet absorption line observations
New measurements of interstellar CN in translucent molecular clouds arepresented. The CN is observed by optical absorption lines in both the B2Sigma(+) violet and A 2Pi - X 2Sigma(+) red systems and through the N =1-0 emission lines at 113.491 GHz. It is shown how the unsaturated linesof the red system can be used to determine the Doppler parameter b andthus to assess the saturation corrections in the analysis of thestronger lines of the violet system. In all cases, the Doppler parameteris small, b less than about 1 km/s, and agrees well with the velocitydispersion obtained from (C-13)O millimeter emission of lines in thesame direction but averaged over a different volume of gas.
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Calibration of the normal color indices (b-y)0 and absolute stellar magnitudes M(V) for A4-F3-class supergiants on the basis of uvby-beta-photometry data
Calibration relations obtained for the color index (b-y)0 = F (/m1/, r)and absolute magnitudes M(V) = M(V) (beta) for high-luminosity stars arepresented. The regions where the calibrations are valid include stars ofspectral types ranging from A4 to F3 and luminosity classes from I toII. The calibration relations are used to estimate the distance moduliof 10 supergiants in the LMC.
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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.
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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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The maximum amplitude of the optical micro-variations of massive O-F type stars (or Alpha Cygni variables, including LBV's or S DOR variables) across the HR diagram
The maximum light amplitude (MLA) of the microvariations of nearly 100massive stars with spectral type O 3-F8 are collected from theliterature and unpublished material. These variables, called the AlphaCygni variables, also include the LBVs or S Dor type variables. The SDor type variables must be in a quiescent stage to detect theirintrinsic variations properly. The log T(eff)/MLA diagram exhibits aclear separation between S Dor type variables and the normal Alpha Cygnivariables (the majority). The results suggest that the outer layers ofboth types of stars where gravity waves presumably occur, differphysically from each other.
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Hot components and circumstellar grains in M supergiant syncretic binaries
Ultraviolet and infrared spectra were obtained in order to study grainsin cool star and hot star syncretic type binaries. Grains are found inonly about half of the syncretic systems. The results suggest thatgrains have not formed in many syncretic systems because of ultravioletradiation from the hot star. Circumstellar extinction could not beunambiguously detected in those systems with grains.
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An investigation of the micro-variations of highly luminous OBA type stars. V
The optical microvariations of eight high luminous stars, five of typeO, two of type B, and one of type A are analyzed. The reddening,temperatures, gravities, and characteristic periods for the stars areestimated. The changes in the light and color curves are discussed. Theamplitude-wavelength relation is studied. It is observed that seven ofthe stars are variable and characteristic periods for only three of thestars are detected in the light curve. The data reveal that theamplitudes of light variations are largest in the ultraviolet for BAtype supergiants; for some O type stars there is little differencebetween the amplitudes at short and long wavelengths.
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Interstellar molecular carbon in distant supergiants
The results of a search for interstellar C2 lines in the spectrum ofsouthern reddened supergiants are reported. The C2 excitation parametersalong the lines of sight to HD 169454 and BD-14 deg 5037, both in theSct OB3 association, have been determined from spectra of high S/N.Radiative excitation effects of high rotational levels were found in HD169454. The C2 lines in BD-14 deg 5037 are clearly double, but only showmarginal deviations from thermal level populations. The column densitiesfor all stars so far observed, except of HD 92693 in Car OB1, appearlinearly correlated with E(B-V). A mean columnar abundance of 3.0 x 10to the -8th is estimated, which agrees with theoretical predictions forthe C2 abundance in dense molecular clouds.
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An investigation of the micro variations of highly luminous OBA type stars. IV
VBLUW photometry of eight OBA type stars of high luminosity, M(001) lessthan -7, is presented. The mean errors of the nightly averages amount toless than or equal to + or - 0.002 mag. All but presumably one appear tobe variable, of which the maximum light amplitude amounts up toapproximately 0.1 mag. The variability of brightness and colors, andtheir time scales (days to weeks) increase with decreasing temperature.
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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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Interstellare C2-Linien in frühen Überriesen
Not Available
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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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VY Carinae, S Normae, and photometric luminosities for bright giants and supergiants of types G and K
Observations in the modified Stromgren system of the Cepheids VY Carinaeand S Normae with their associated early-type stars are discussed. Theluminosities of the Cepheids, together with the bright giants R Puppis,HR 2834, HR 4180, and HDE 269953 in the Large Magellanic Cloud (LMC),are used for calibration of photometric luminosities.
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Estimation of spectral classifications for bright southern stars with interesting Stromgren indices
This paper investigates the degree of success with which uvby photometrycan be applied to predict spectral classifications for 947 A, F, and Gstars brighter than an apparent magnitude of 8.3 and with four-colorindices indicating some kind of interesting, unusual, or peculiarspectrum. One or several possible spectral classifications are estimatedfor each star from photometry alone, double stars are distinguished, andthe estimates are compared with published classifications. The resultsshow that the framework provided by uvby photometry can be extended toinclude most G and K stars, reddened stars, peculiar stars, and certaintypes of double star.
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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
