Strömgren H? Photometry of O and B Stars in Norma
This investigation presents a study of the Galactic structure toward theNorma section of the Milky Way. The field studied is located between325° and 335° Galactic longitude and -8° to 8° Galactic latitude. New observations in the uvby? system are combined with all uvby? data currently available to collate a sample of 130 O and B stars. A uniform procedure is applied to obtain the color excesses and stellardistances for all of the stars in the sample. The sample is magnitudelimited to about V=9.5 mag and contains the brightest stars of the openclusters NGC 6087 and Ly 6, the field 2158 of Loden, the OB associationNor OB1, and stars located in the directions of R 103 and R 105. Theintrinsically luminous stars in the field studied appear to be closer tothe Sun than it has previously been thought. At about 860 pc, themajority of the stars in the sample delineate a segment consistent withthe location of the Sagittarius-Carina arm as suggested in the four-armmodel representation of the grand design of the Milky Way. A small partof the sample defines the near edge of the Scutum-Crux arm at about 1.75kpc.
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Multi-wavelength observations of Galactic hard X-ray sources discovered by INTEGRAL. II. The environment of the companion star
Context: The INTEGRAL mission has led to the discovery of a new type ofsupergiant X-ray binaries (SGXBs), whose physical properties differ fromthose of previously known SGXBs. Those sources are in the course ofbeing unveiled by means of multi-wavelength X-rays, optical, near- andmid-infrared observations, and two classes are appearing. The firstclass consists of obscured persistent SGXBs and the second is populatedby the so-called supergiant fast X-ray transients (SFXTs). Aims:We report here mid-infrared (MIR) observations of the companion stars oftwelve SGXBs from these two classes in order to assess the contributionof the star and the material enshrouding the system to the totalemission. Methods: We used data from observations we carried outat ESO/VLT with VISIR, as well as archival and published data, toperform broad-band spectral energy distributions of the companion starsand fitted them with a combination of two black bodies representing thestar and a MIR excess due to the absorbing material enshrouding thestar, if there was any. Results: We detect a MIR excess in theemission of IGR J16318-4848, IGR J16358-4726, and perhaps IGRJ16195-4945. The other sources do not exhibit any MIR excess even whenthe intrinsic absorption is very high. Indeed, the stellar winds ofsupergiant stars are not suitable for dust production, and we show thatthis behaviour is not changed by the presence of the compact object.Concerning IGR J16318-4848 and probably IGR J16358-4726, the MIR excesscan be explained by their sgB[e] nature and the presence of anequatorial disk around the supergiant companion in which dust can beproduced. Moreover, our results suggest that some of the supergiantstars in those systems could exhibit an absorption excess compared toisolated supergiant stars, this excess being possibly partly due to thephotoionisation of their stellar wind in the vicinity of theiratmosphere. We also show that the differences in behaviour between theobscured SGXBs and the SFXTs in the high-energy domain do not exist fromoptical-to-MIR wavelength. Supergiant stars in SFXTs could neverthelessbe most of the time less absorbed than supergiant stars in obscuredSGXBs, due to the geometry of the systems. At last, our results confirma very dense cocoon of material around the compact object as theextinction in the X-ray domain is generally several orders of magnitudehigher than the extinction in the visible.Based onobservations carried out at the European Southern Observatoryunder programmes ID 075.D-0773 and 077.D-0721.
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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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The total-to-selective extinction ratio determined from near IR photometry of OB stars
The paper presents an extensive list of the total to selectiveextinction ratios R calculated from the infrared magnitudes of 597 O andB stars using the extrapolation method. The IR magnitudes of these starswere taken from the literature. The IR colour excesses are determinedwith the aid of "artificial standards" - Wegner (1994). The individualand mean values of total to selective extinction ratios R differ in mostcases from the average value R=3.10 +/-0.05 - Wegner (1993) in differentOB associations. The relation between total to selective extinctionratios R determined in this paper and those calculated using the "methodof variable extinction" and the Cardelli et al. (1989) formulae isdiscussed. The R values presented in this paper can be used to determineindividual absolute magnitudes of reddened OB stars with knowntrigonometric parallaxes.
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Observations of OB-stars at the former Leiden Southern Station
About 700 stars, mostly OB-stars, were observed by the author at theformer Leiden Southern Station at Hartebeespoortdam, South Africa, inthe observing seasons 1965, 1968, 1969, 1974, 1977, 1978. Observationswere made in the five channels of the Walraven photometric system. Dueto weathering of the telescope mirror the W channel gave no reliableresults for the faintest stars (m = 11 mag); in these cases the U-Wcolour index is not given. The change in sensitivity in the V channel,supposedly having occurred in 1968, was not recognised. Table~5 is onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/369/527
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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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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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An Einstein Observatory SAO-based catalog of B-type stars
About 4000 X-ray images obtained with the Einstein Observatory are usedto measure the 0.16-4.0 keV emission from 1545 B-type SAO stars fallingin the about 10 percent of the sky surveyed with the IPC. Seventy-fourdetected X-ray sources with B-type stars are identified, and it isestimated that no more than 15 can be misidentified. Upper limits to theX-ray emission of the remaining stars are presented. In addition tosummarizing the X-ray measurements and giving other relevant opticaldata, the present extensive catalog discusses the reduction process andanalyzes selection effects associated with both SAO catalog completenessand IPC target selection procedures. It is concluded that X-rayemission, at the level of Lx not less than 10 exp 30 ergs/s, is quitecommon in B stars of early spectral types (B0-B3), regardless ofluminosity class, but that emission, at the same level, becomes lesscommon, or nonexistent, in later B-type stars.
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UBV photometry of OB+ stars in the southern Milky Way
One thousand two hundred and twenty six new observations are combinedwith previously published results of the author to yield an internalyconsistent set of magnitudes and colors on the international UBV systemfor 666 stars classified as OB+ in the Stephenson-Sanduleak OB starsurvey. The U - B, B - V diagram indicates that these stars consistprimarily of O-type stars and early B-type supergiants, reddened by upto E(B - V) = 2.1 mag.
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Observations of the very broad-band structure by combined UVBY and UBV photometry
The features of the very broad-band structure (VBS) in the interstellarextinction curve were studied photometrically. It is shown that thecolor excess ratio E(b-y)/E(B-V) can be used as a measure of thestrength of the VBS. The color excess ratio was calibrated in terms ofthe central depth of the VBS; from the calibration stars and 13 reddenedyoung open clusters containing more than 10 B-type stars, a relationshipwas derived between the central depth of the VBS and the E(B-V)quantity.
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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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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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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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New UBVRI photometry for 900 supergiants
A description is presented of the results obtained in connection with asystematic program of supergiant photometry on the Johnson UBVRI system.During the eight years after the start of the program, almost 1000 starshave been observed, about 400 three or more times each. The originalselection of stars used the spectral type catalog of Jaschek et al.(1964) to choose supergiants. Since observations were possible from bothChile and Canada, no declination limits were imposed, and no particularselection criteria were imposed other than to eliminate carbon stars.These are so red as to require enormous extrapolations of thetransformation equations.
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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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Variability and mass loss in IA O-B-A supergiants
Recently completed catalogs of MK spectral types and UBV photometry of1227 OB stars in the southern Milky Way have been analyzed toinvestigate brightness and color variability among the Ia supergiants.It is found that brightness variability is common among the O9-B1supergiants with typical amplitudes about 0.1 and time scales longerthan a week and shorter than 1000 days. Among the A supergiantsfluctuations in U-B color are found on similar time scales and withamplitude about 0.1. For many early Ia supergaints there is a poorcorrelation between Balmer jump and spectral type, as had been knownpreviously. An attempt to correlate the Balmer jump deficiency with massloss rate yielded uncertain results.
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Very broadband structure in the extinction curves of southern Milky Way stars
Very broadband structure (VBS), previously detected in the interstellarextinction curve, is examined in detail for 22 reddened stars in thesouthern Milky Way. The VBS, which takes the form of a shallowdepression in the 5200-6000 A region, appears to be a widespread featureof the general galactic extinction, with the central depth amounting toabout 0.02 mag per magnitude of visual extinction for stars with longpath-length reddening. Two stars in the Rho Ophiuchi dark cloud exhibita modified form of VBS which may reflect chemical changes occurring onthe grain surfaces. A possible identification of the VBS with solidmagnetite (Fe3O4) in the grain material is discussed.
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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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On the 4430 A interstellar band - A visual classification
A system of visual classification of the strength of the interstellarband 4430 A has been developed, based on spectra taken at spectralclassification dispersion. The intensity of the band was divided into 8main classes, defined by a group of selected standard stars. The systemwas applied to 1,111 southern OB stars contained in the catalog ofspectral types by Garrison, Hiltner, and Schild (1977). The mean errorin the classification was estimated to be plus or minus 1 class.Equivalent widths were measured for 100 stars; an excellent correlationwith the visual estimations was obtained. A calibration between thesetwo parameters is given.
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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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Observations in linearly polarized light of the intensity of the diffuse lam 6180 absorption band in 56 southern O, B and A stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978A&A....70..195G&db_key=AST
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The reddening law in Carina OB 1
RI magnitudes of 68 stars in the Carina OB 1 stellar association and of11 comparison early-type stars were measured photoelectrically. Thisphotometry, combined with previously published UBV observations andspectral types, confirms the existence of higher-than-normalcolor-excess ratios, localized in the central regions of theassociation. An abnormal interstellar extinction law seems to bepresent, and the ratio of total to selective absorption is estimated andused to rediscuss the photometric distance modulus.
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MK spectral classifications for southern OB stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977ApJS...35..111G&db_key=AST
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Infrared photometry, extinction curves and R values for stars in the southern Milky Way.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976MNRAS.177..625W&db_key=AST
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