On the Formation of Perseus OB1 at High Galactic Latitudes
The Per OB1 association, which contains the remarkable double cluster hand χ Per, is unusual in not having a giant molecular cloud in itsvicinity. We show from Hipparcos data that the luminous members of thisassociation exhibit a bulk motion away from the Galactic plane, suchthat their average velocity increases with height above the Galacticplane. We find HAeBe and T Tauri stars toward probable remnant molecularclouds associated with Per OB1. These star-forming regions lie wellbeyond the location of the luminous member stars at heights of 280-400pc above the Galactic plane, far higher than that previously found forembedded clusters. We argue that the observed motion of the luminousmember stars is most naturally explained if many formed from moleculargas pushed and accelerated outward by an expanding superbubble, drivenpresumably by stellar winds and perhaps also by supernova explosions. Alarge shell of atomic hydrogen gas and dust that lies just beyond theremnant molecular clouds, believed to be driven by just such asuperbubble, may comprise the swept-up remains of the parental giantmolecular cloud from which this association formed. In support of thispicture, we find a weak trend for the younger O star members to lie athigher Galactic latitudes than the older supergiant members. Thestar-forming regions located at even larger heights above the Galacticplane presumably correspond to more recent episodes of star formation ator near the periphery of this superbubble.
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An Analysis of the Shapes of Interstellar Extinction Curves. V. The IR-through-UV Curve Morphology
We study the IR-through-UV interstellar extinction curves towards 328Galactic B and late-O stars. We use a new technique which employsstellar atmosphere models in lieu of unreddened "standard" stars. Thistechnique is capable of virtually eliminating spectral mismatch errorsin the curves. It also allows a quantitative assessment of the errorsand enables a rigorous testing of the significance of relationshipsbetween various curve parameters, regardless of whether theiruncertainties are correlated. Analysis of the curves gives the followingresults: (1) In accord with our previous findings, the central positionof the 2175 A extinction bump is mildly variable, its width is highlyvariable, and the two variations are unrelated. (2) Strong correlationsare found among some extinction properties within the UV region, andwithin the IR region. (3) With the exception of a few curves withextreme (i.e., large) values of R(V), the UV and IR portions of Galacticextinction curves are not correlated with each other. (4) The largesightline-to-sightline variation seen in our sample implies that anyaverage Galactic extinction curve will always reflect the biases of itsparent sample. (5) The use of an average curve to deredden a spectralenergy distribution (SED) will result in significant errors, and arealistic error budget for the dereddened SED must include the observedvariance of Galactic curves. While the observed largesightline-to-sightline variations, and the lack of correlation among thevarious features of the curves, make it difficult to meaningfullycharacterize average extinction properties, they demonstrate thatextinction curves respond sensitively to local conditions. Thus, eachcurve contains potentially unique information about the grains along itssightline.
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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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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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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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The threshold for stellar winds in hot main-sequence stars
The profiles of ultraviolet resonance lines of C IV were surveyed in asample of 29 cluster and association members in the spectral type rangeO9-B2 III-V, together with a few field stars of interest. Thetemperatures and gravities of the stars were taken from the modelatmosphere analysis by Grigsby, Morrison, & Anderson (1992), and theluminosities were estimated on the basis of cluster and associationdistances from the recent literature. A parameter Pw wasdefined in order to describe the degree and assymetry of the C IVprofile. This parameter, together with total C IV equivalent width, wasfound to be well correlated with stellar luminosity and temperature. Afew anomalous stars were noted: tau Sco, HD 66665, HD 13621, and the ONstars HD12323 and HD 201345. The results suggest a sudden onset ofobservable mass loss at T(effective) = 27,500 +/- 500 K, log (L/solarluminosity) = 4.4 +/- 0.12, in agreement with the previous study byPrinja (1989). At T(effective) = 28,000 K and log g = 4, our non-LTEmodel atmospheres show an enhancement in the ground-state population ofC(+3) in their topmost layer, which could be responsible for initiationof the winds via radiation pressure on the C(+3) ions, or for the onsetof visibility of C(+3) ions in the wind because of an increase in theoptical depth in the C IV lines in the outermost layers.
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An IUE survey of interstellar H I LY alpha absorption. 1: Column densities
We measure Galactic interstellar neutral hydrogen column densities byanalyzing archival interstellar Ly alpha absorption line data toward 554B2 and hotter stars observed at high resolution with the IUE satellite.This study more than doubles the number of lines of sight with measuresof N(H I) based on Ly alpha. We have included the scattered lightbackground correction algorithm of Bianchi and Bohlin in our datareduction. We use the correlation between the Balmer discontinuity(c1) index and the stellar Ly alpha absorption in order toassess the effects of stellar Ly alpha contamination. Approximately 40%of the B stars with measured (c1) index, exhibit seriousstellar Ly alpha contamination. One table contains the derived values ofthe interstellar N(H I) for 393 stars with at most small amounts ofstellar contamination. Another lists the observed values of total N(H I)for 161 stars with suspected stellar Ly alpha contamination and/oruncertain stellar parameters.
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Environment Dependence of Interstellar Extinction Curves
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...274..439J&db_key=AST
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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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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.
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Non-LTE, line-blanketed model atmospheres for late O- and early B-type stars
The use of non-LTE line-blanketed model atmospheres to analyze thespectra of hot stars is reported. The stars analyzed are members ofclusters and associations, have spectral types in the range O9-B2 andluminosity classes in the range III-IV, have slow to moderate rotation,and are photometrically constant. Sampled line opacities of iron-groupelements were incorporated in the radiative transfer solution; solarabundances were assumed. Good to excellent agreement is obtained betweenthe computed profiles and essentially all the line profiles used to fixthe model, and reliable stellar parameters are derived. The synthetic MII 5581 equivalent widths agree well with the observed ones at the lowend of the temperature range studied, but, above 25,000 K, the syntheticline is generally stronger than the observed line. The behavior of theobserved equivalent widths of N II, N III, C II and C III lines as afunction of Teff is studied. Most of the lines show much scatter, withno consistent trend that could indicate abundance differences from starto star.
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Distribution and motions of OB stars in the direction of H and KHI Perseus.
Not Available
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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.
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The Distribution of Early Type Stars in the Direction of Stellar Associations PERSEUS-OB1 SCORPIUS-OB1 and CYGNUS-OB1
Not Available
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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.
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Atlas of the wavelength dependence of ultraviolet extinction in the Galaxy
The paper presents a collection of 115 extinction curves derived fromlow-dispersion IUE spectra. The spectra have been reduced with the useof techniques designed to reduce the effects of random noise and theinfluence of residual spectral features due to classification mismatch.The magnitudes of other instrumental and interpretational uncertaintiesare estimated. The extinction curves are presented with normalization toE(B-V) = 1 and the FUV portion (below 170 nm) is also shown for E(13-17)= 1. The atlas includes examples of extinction originating in thediffuse medium and several major nebulae and dense clouds.
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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.
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Observations of interstellar diffuse absorption band at 4430 A
Observations of the interstellar diffuse absorption band at 4430 A for800 O and B stars in Neckel's (1967) catalog are being carried out, and482 spectra obtained up to September 1983 have been reduced. It isconfirmed that the strength of the interstellar diffuse absorption bandat 4430 A does not simply relate to the abundance of interstellar grainson the line of sight. The relation between the color excess E(B-V) andthe equivalent width of the band to the direction of l = 130-140 deg andb = -5 to +5 deg shows that some parameter(s) other than E(B-V) is (are)needed to understand the cause of this band.
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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.
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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.
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Meridian observations made with the Carlsberg Automatic Meridian Circle at Brorfelde (Copenhagen University Observatory) 1981-1982
The 7-inch transit circle instrument with which the present position andmagnitude catalog for 1577 stars with visual magnitudes greater than11.0 was obtained had been equipped with a photoelectric moving slitmicrometer and a minicomputer to control the entire observationalprocess. Positions are reduced relative to the FK4 system for each nightover the whole meridian rather than the usual narrow zones. Thepositions of the FK4 stars used in the least squares solution are alsogiven in the catalog.
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Kinematic properties of supergiants in the Perseus spiral arm
Analysis of the space motions of supergiants in the Perseus arm regionindicates that the stellar peculiar-velocity field has a large-scalenonuniformity probably resulting both from the presence of sizablegroups of young stars and from systematic motions in the arm aspredicted by density-wave theory. Proper motions are tabulated for 78stars.
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A magnitude limited stellar X-ray survey and the F star X-ray luminosity function
An X-ray survey has been conducted of stars brighter than visualmagnitude 8.5 that have serendipitously fallen into the fields of viewof the Imaging Proportional Counter of the Einstein Observatory. Thesurvey includes 227 separate 1 x 1 deg fields, containing 274 stars witha visual magnitude of no more than 8.5 and covering a wide range ofspectral types and luminosity classes. X-ray emission was detected from33 stars, and upper limits have been determined for the remainder of thesample. F type stars dominate the detected sample, and most of these areshown to be dwarfs. An X-ray luminosity function for dF stars has beendeduced, and reveals that the average 0.2-4.0 keV luminosity of thesestars is around 10 to the 29th erg/sec. Constraints have been placed onthe high luminosity tails and medians of the X-ray luminosity functionsfor other types of stars.
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Four-color and H-beta photometry for O-A0 type stars in three regions near the galactic equator
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1982A&AS...49..561W&db_key=AST
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Interstellar extinction in the Perseus arm
Individual UV extinction curves for nine stars located in the directionof h and Chi Persei in the distance range 0.6-4.4 kpc are presented. Theobservations were made with the International Ultraviolet Explorer (IUE)in the low dispersion mode with large aperture. The sample has beenenlarged by the use of available UV and visible data for 32 reddenedstars with distances r not less than 2 kpc located in the samedirection. It is found that the mean interstellar extinction curve forthe stars located in the Perseus arm shows significantly higherextinction shortward of 2000 A than the galactic mean.
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Stellar Rotation and be Stars in the H and χ Persei Association
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968ApJ...154..933S&db_key=AST
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Measurements of the strength of Hα in 951 early-type stars
Not Available
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On Beta Cephei Stars: a Search for Beta Cephei Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1967ApJS...14..263H&db_key=AST
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Catalogue d'etoiles O et B.
Not Available
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INHABITED SKY
