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A Medium Resolution Near-Infrared Spectral Atlas of O and Early-B Stars
We present intermediate-resolution (R~8000-12,000) high signal-to-noise(S/N) H- and K-band spectroscopy of a sample of 37 optically visiblestars, ranging in spectral type from O3 to B3 and representing mostluminosity classes. Spectra of this quality can be used to constrain thetemperature, luminosity, and general wind properties of OB stars, whenused in conjunction with sophisticated atmospheric model codes. Mostimportant is the need for moderately high resolutions (R>=5000) andvery high signal-to-noise (S/N>=150) spectra for a meaningful profileanalysis. When using near-infrared spectra for a classification system,moderately high signal-to-noise (S/N~100) is still required, though theresolution can be relaxed to just a thousand or two. In the Appendix weprovide a set of very high-quality near-infrared spectra of Brackettlines in six early-A dwarfs. These can be used to aid in the modelingand removal of such lines when early-A dwarfs are used for telluricspectroscopic standards.
| Quantitative H and K band spectroscopy of Galactic OB-stars at medium resolution
In this paper we have analyzed 25 Galactic O and early B-stars by meansof H and K band spectroscopy, with the primary goal to investigate towhat extent a lone near-IR spectroscopy is able to recover stellar andwind parameters derived in the optical. Most of the spectra have beentaken with subaru-ircs, at an intermediate resolution of 12 000, andwith a very high S/N, mostly on the order of 200 or better. In order tosynthesize the strategic H/He lines, we have used our recent,line-blanketed version of fastwind (Puls et al. 2005, A&A, 435,669). In total, seven lines have been investigated, where for two starswe could make additional use of the Hei2.05 singlet which has beenobserved with irtf-cshell. Apart from Brγ and Heii2.18, the otherlines are predominately formed in the stellar photosphere, and thusremain fairly uncontaminated from more complex physical processes,particularly clumping. First we investigated the predicted behaviour ofthe strategic lines. In contradiction to what one expects from theoptical in the O-star regime, almost all photospheric H/Hei/Heii H/Kband lines become stronger if the gravity decreases. Concerning H andHeii, this finding is related to the behaviour of Stark broadening as afunction of electron density, which in the line cores is different formembers of lower (optical) and higher (IR) series. Regarding Hei, thepredicted behaviour is due to some subtle NLTE effects resulting in astronger overpopulation of the lower level when the gravity decreases.We have compared our calculations with results from the alternative NLTEmodel atmosphere code cmfgen (Hillier & Miller 1998, ApJ, 496, 407).In most cases, we found reasonable or nearly perfect agreement. Only theHei2.05 singlet for mid O-types suffers from some discrepancy, analogouswith findings for the optical Hei singlets. For most of our objects, weobtained good fits, except for the line cores of Brγ in earlyO-stars with significant mass-loss. Whereas the observations showBrγ mostly as rather symmetric emission lines, the models predicta P Cygni type profile with strong absorption. This discrepancy (whichalso appears in lines synthesized by cmfgen) might be an indirect effectof clumping. After having derived the stellar and wind parameters fromthe IR, we have compared them to results from previous optical analyses.Overall, the IR results coincide in most cases with the optical oneswithin the typical errors usually quoted for the correspondingparameters, i.e., an uncertainty in T_eff of 5%, in log g of 0.1 dex andin {dot M} of 0.2 dex, with lower errors at higher wind densities.Outliers above the 1-σ level where found in four cases withrespect to log g and in two cases for {dot M}.
| HD 183143: A Hypergiant
We present spectroscopic evidence that the luminosity of HD 183143 ishigher by one magnitude than thought previously. The star is yet anotherB6-8 Ia-0 white hypergiant of the Galaxy. Its absolute visual magnitudeis close to -8 mag, and its distance is close to 2 kpc. We describespectroscopic manifestations of the nonstationary behavior of itsatmosphere and wind.
| The wind momentum-luminosity relationship of galactic A- and B-supergiants
The Balmer lines of four A Ia-supergiants (spectral type A0 to A3) andfourteen B Ia and Ib-supergiants (spectral type B0 to B3) in the solarneighbourhood are analyzed by means of NLTE unified model atmospheres todetermine the properties of their stellar winds, in particular theirwind momenta. As in previous work for O-stars (Puls et al. \cite{pul96})a tight relationship between stellar wind momentum and luminosity(``WLR'') is found. However, the WLR varies as function of spectraltype. Wind momenta are strongest for O-supergiants, then decrease fromearly B (B0 and B1) to mid B (B1.5 to B3) spectral types and becomestronger again for A-supergiants. The slope of the WLR appears to besteeper for A- and mid B-supergiants than for O-supergiants. Thespectral type dependence is interpreted as an effect of ionizationchanging the effective number and the line strength distributionfunction of spectral lines absorbing photon momentum around the stellarflux maximum. This interpretation needs to be confirmed by theoreticalcalculations for radiation driven winds. The ``Pistol-Star'' in theGalactic Centre, an extreme mid B-hypergiant recently identified as oneof the most luminous stars (Figer et al. \cite{fig99}) is found tocoincide with the extrapolation of the mid B-supergiant WLR towardshigher luminosities. However, the wind momentum of the Luminous BlueVariable P Cygni, a mid B-supergiant with extremely strong mass-loss, is1.2 dex higher than the WLR of the ``normal'' supergiants. Thissignificant difference is explained in terms of the well-known stellarwind bi-stability of supergiants very close to the Eddinton-limit inthis particular range of effective temperatures. A-supergiants in M31observed with HIRES at the Keck telescope have wind momenta compatiblewith their galactic counterparts. The potential of the WLR as a new,independent extragalactic distance indicator is discussed. It isconcluded that with ten to twenty objects, photometry with HST andmedium resolution spectroscopy with 8m-telescopes from the grounddistance moduli can be obtained with an accuracy of about 0fm1 out tothe Virgo and Fornax clusters of galaxies.
| Galactic B-supergiants: A non-LTE model atmosphere analysis to estimate atmospheric parameters and chemical compositions
A non-LTE model atmosphere analysis of moderate resolution (R ~ 5 000)spectra of 46 Galactic B-type supergiants is presented. Standardtechniques are adopted, viz. plane-parallel geometry and radiative andhydrostatic equilibrium. Spectroscopic atmospheric parameters (T_eff,log g & v_turb) and chemical abundances (He, C, N, O, Mg & Si)are estimated, both as a test of the validity of such an approach and inan attempt to provide consistent results for supergiants covering asignificant range of spectral types. The values of the estimatedatmospheric parameters and their dependence on the physics adopted inthe model atmospheres calculations are discussed. The absolute metalabundances are compared to those of main sequence B-type stars and, ingeneral, their chemical compositions appear to be similar. Theabundances for He, C, N & O are considered in some detail and arediscussed in the context of possible evolutionary histories for thisstellar sample. Specifically, it is found that the supergiant sample canbe subdivided into a number of evolutionarily distinct groups. The lowermass objects are predominantly chemically near-normal i.e. theirphotospheres show little or no evidence for chemical processing, whereasthe higher mass supergiants have CNO ratios which are indicative of CNand possibly NO-cycle burning. An attempt is made to quantify thedifference in nitrogen and carbon abundances between the high and lowmass targets but this is hampered by theoretical uncertainties. Thepossibilities that the most highly processed supergiants may have eitherlarger rotational velocities or have undergone mass transfer within abinary system are discussed.
| Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS
Radial velocities have been determined for a sample of 2930 B2-F5 stars,95% observed by the Hipparcos satellite in the north hemisphere and 80%without reliable radial velocity up to now. Observations were obtainedat the Observatoire de Haute Provence with a dispersion of 80Ä,mm(-1) with the aim of studying stellar and galactic dynamics.Radial velocities have been measured by correlation with templates ofthe same spectral class. The mean obtained precision is 3.0 km s(-1)with three observations. A new MK spectral classification is estimatedfor all stars. Based on observations made at the Haute ProvenceObservatory, France and on data from The Hipparcos Catalogue, ESA.Tables 4, 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr or viahttp://cdsweb.u-strasbg.fr/Abstract.htm
| 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.
| Equivalent width of NA I and K I lines and reddening.
The profile, radial velocity and equivalent width of the interstellarlines of Na I (5890.0, 5895.9Å) and K I (7699.0Å) have beenobtained from Echelle+CCD observations at resolving powerλ/{DELTA}λ~16,500 for 32 O and early B stars sufferingfrom a reddening between E_B-V_=0.06 and 1.57. The data have been usedto search for and calibrate a relation between equivalent width andreddening. When the interstellar lines show a single and sharpcomponent, useful relations to estimate reddening from equivalent widthshave been derived. The relation for Na I is most sensitive in the range0.0<=E_B-V_<=0.4, and the one for K I takes over at higherreddening. Good quality equivalent width measurements allow E_B-V_ to beestimated with an accuracy of about 0.05 mag. For multi-componentprofiles of Na I and K I lines the estimate of reddening is moreambiguous with a general scatter of 0.15mag. Close blends of multiplecomponents allow only an estimate of an upper limit to E_B-V_.
| Cross-correlation characteristics of OB stars from IUE spectroscopy
We present a catalogue of homogeneous measures of the linewidthparameter, v_esin i, for 373 O-type stars and early B supergiants(including the separate components of 25 binary and three triplesystems), produced by cross-correlating high-resolution,short-wavelength IUE spectra against a `template' spectrum of tauSco. Wealso tabulate terminal velocities. There are no O supergiants in oursample with v_esin i<65 km s^-1, and only one supergiant earlier thanB5 has v_esin i<50 km s^-1, confirming that an important linebroadening mechanism in addition to rotation must be present in theseobjects. A calibration of the area under the cross-correlation peakagainst spectral type is used to obtain estimates of continuum intensityratios of the components in 28 spectroscopically binary or multiplesystems. At least seven SB2 systems show evidence for the `Struve-Sahadeeffect', a systematic variation in relative line strength as a functionof orbital phase. The stellar wind profiles of the most rapid rotator inour sample, the O9III:n* star HD 191423 (v_esin i=436km s^-1), show itto have a `wind-compressed disc' similar to that of HD 93521; this starand other rapid rotators are good candidates for studies of non-radialpulsation.
| 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.
| Intrinsic colour indices of O- and B- type stars in the Vilnius photometric system.
Not Available
| Galactic B-supergiants. II - Line strengths in the visible: Evidence for evolutionary effects?
Following the discovery by Lennon et al. (1992) of anomalously weakcarbon lines in the Galactic B-supergiants, a search was conducted forthe signatures of CNO processed material in the atmospheres of thesestars. It was found that the NII line strengths around spectral type B2correlate with luminosity, but exhibit a clear anticorrelation with theCII lines. It is suggested that this trend may be evidence for CNOprocessed material contaminating the atmospheres of the most luminousstars. The CNO processing signature was found to be most pronounced inthe more luminous supergiants, in qualitative agreement with stellarevolution calculations (provided that such stars have passed through aprevious red-supergiant phase of evolution).
| The chemical composition of B-supergiant atmospheres
Not Available
| Galactic B-supergiants. I - an atlas of O9-B9 supergiant spectra from 3950 A to 4950 A
CCD spectra are presented for supergiants of spectral types O9-B9 andluminosity subclasses Ia and Ib. They cover the wavelength region fromapproximately 3950 A to 4950 A at a resolution of 0.8 A, and normallyhave a signal-to-noise in excess of 150 at 4600 A. The spectra arediscussed in respect to their classification. A number of stars showclear evidence of the 'filling in' of hydrogen lines by emission fromthe stellar wind, while HD 190603, a B1.5 Ia(+) hypergiant, exhibits anH-beta P-Cygni type line-profile. Also reported is the finding of a newnitrogen weak star, HD 13866, in the Per OB1 association which isclassified here as BC2 Ib.
| Galactic OB associations in the northern Milky Way Galaxy. I - Longitudes 55 deg to 150 deg
The literature on all OB associations was reviewed, and their IRAS pointsource content was studied, between galactic longitude 55 and 150 deg.Only one third of the 24 associations listed by Ruprecht et al. (1981)have been the subject of individual studies designed to identify thebrightest stars. Distances to all of these were recomputed using themethod of cluster fitting of the B main sequence stars, which makes itpoossible to reexamine the absolute magnitude calibration of the Ostars, as well as for the red supergiant candidate stars. Also examinedwas the composite HR diagram for these associations. Associations withthe best defined main sequences, which also tend to contain very youngclusters, referred to here as OB clusters, have extremely few evolved Band A or red supergiants. Associations with poorly defined mainsequences and few OB clusters have many more evolved stars. They alsoshow an effect in the upper HR diagram referred to as a ledge byFitzpatrick and Garmany (1990) in similar data for the Large MagellanicCloud. It is suggested that the differences in the associations are notjust observational selection effects but represent real differences inage and formation history.
| Groups of stars with common motion in the Galaxy. Groups of O and B stars
Not Available
| Absolute magnitudes of B emission line stars - Correlation between the luminosity excess and the effective temperature
A new determination of the visual absolute magnitude of Be stars iscarried out. For this, a new calibration of visual absolute magnitudesof B stars of luminosity classes, V, IV, and III is first obtained froma sample of 215 stars. The absolute luminosity excess in the visual isdetermined for a sample of 49 Be stars. It is found that this excess iscorrelated with the effective temperature of the underlying stars. Awell defined correlation between this excess and the emission in thefirst two Balmer lines is established. From these results, using asimple model of circumstellar envelope, it is inferred that the zones ofthe circumstellar envelope contributing to the emission in the continuumand in the lines have to be rather small. It is also deduced that theemission measure of the envelope is correlated with the temperature ofthe central star and that the irregular photometric variations of Bestars are an envelope-opacity phenomenon.
| Distribution and motions of OB stars in the direction of H and KHI Perseus.
Not Available
| Early-type stars in the stellar associations Per OB1, SCO OB1, and CYG OB1 by observations with space telescope 'Glazar'
This paper presents results of observations at 1640 A carried out inSeptember 1988 with the Soviet space telescope Glazar on the regions ofstellar associations Per OB1, Sco OB1, and Cyg OB1. Thirty twophotographs were obtained, on which 94 images of stars were identifiedand measured. In stellar associations Per OB1, Sco OB1, and Cyg OB1, 42,22, and 30 hot stars brighter than 10 mag at 1640 A were detected,respectively. A comparison of Glazar measurements of stellar magnitudeswith those available from TD-1 telescope measurements and from ANSmeasurements showed reasonably good agreement.
| Photospheric Absorption Lines in the Ultraviolet Spectra of O-Stars and B-Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990MNRAS.246..392P&db_key=AST
| The Distribution of Early Type Stars in the Direction of Stellar Associations PERSEUS-OB1 SCORPIUS-OB1 and CYGNUS-OB1
Not Available
| A list of MK standard stars
Not Available
| 2000 A UV imaging of a 6 deg diameter field around the H and Chi Persei double cluster
A stellar field centered close to the h and Chi per double cluster hasbeen observed at 2000 A by the stratospheric balloon-born telescope ofthe SCAP-2000 program. It is shown that the prevailing extinction lawproduces greater extinction at 1965 A than is predicted by the meanextinction law. The results suggest the presence of an H2 cloud in frontof h and Chi Per in the second absorbing layer and in the local arm. Agroup of hot stars centered at the same distance as the molecular cloudmay form an association of OB stars in the local arm.
| Multivariate statistical analysis of OB stars around H and Chi Persei
A multivariate statistical analysis has been carried out on 49 OB starshaving radial velocities and distance moduli in a field around h and ChiPersei. A hierarchical cluster analysis, combined with discriminantanalysis, has revealed the probable presence of two groups: onebelonging to the Perseus spiral arm (mean distance 2100 pc), the otherlocated at a distance of 1150 pc. Comparison of the difference in meanradial velocities of the groups with the value predicted by the formulaof Oort also supports the result obtained.
| Small Magellanic Cloud: H-gamma-line equivalent widths and luminosity classes of the brightest blue star members
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1987A&AS...69..421A&db_key=AST
| Interdependence of the 4430 A diffuse interstellar band, polarization, and ultraviolet extinction
Central intensities of the 4430-A diffuse interstellar band (DIB) areobtained from reticon spectra of 128 early-type stars, and stars in thePerseus OB1 association are found to have higher ratios of polarizationand weaker 4430-A intensities than do the stars in Cepheus OB3. Thecorrelation noted for OB1 between the A(4430) residuals and E(15-18) canbe explained if the 4430-A DIB arises in a thin grain mantle and the2200-A feature arises in the grain core. The absence of a 4430-A DIB inhigh-Galactic-latitude clouds would then be due to a lack of mantle. TheDIB ratio 5780/5797 A is found to resemble the behavior of the(4430-A)/E(B-V) ratio for seven stars from a range of Galacticlatitudes, confirming the existence of three previously identifiedfamilies of DIBs.
| Catalog of O-B stars observed with Tokyo Meridian Circle
A catalog of the O-B stars, selected from 'Blaauw-Parenago' list andRubin's catalog, has been compiled on the FK4 system by the observationsmade with Gautier 8-inch Meridian Circle at the Tokyo AstronomicalObservatory during the period, 1971 to 1979. It contains 1059 stars andwas compiled for the future establishment of high precision propermotions of O-B stars.
| The local system of early type stars - Spatial extent and kinematics
Published uvby and H-beta photometric data and proper motions arecompiled and analyzed to characterize the structure and kinematics ofthe bright early-type O-A0 stars in the solar vicinity, with a focus onthe Gould belt. The selection and calibration techniques are explained,and the data are presented in extensive tables and graphs and discussedin detail. The Gould belt stars of age less than 20 Myr are shown togive belt inclination 19 deg to the Galactic plane and node-lineorientation in the direction of Galactic rotation, while the symmetricaldistribution about the Galactic plane and kinematic properties (purecircular differential rotation) of the belt stars over 60 Myr oldresemble those of fainter nonbelt stars of all ages. The unresolveddiscrepancy between the expansion observed in the youngest nearby starsand the predictions of simple models of expansion from a point isattributed to the inhomogeneous distribution of interstellar matter.
| Distribution of OB stars and absorbing matter in the region of the association per OB1
The results are given of spectrophotometric investigation of 86 OB starsin the region of the association Per OB1. The blue (4000-4800 A)absolute spectrophotometric gradients, the color excesses, and thedistances of these stars were determined. Analysis of the obtainedresults makes it possible to draw the following conclusions: (1) thecenters of the OB clusters h and Chi Per apparently have a separation ofabout 1000 parsec along the line of sight; (2) the absorbing matter inthe direction of the association Per OB1 is concentrated in the regionsoccupied by the OB stars.
| 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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