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E-BOSS: an Extensive stellar BOw Shock Survey. I. Methods and first catalogue
Context. Bow shocks are produced by many astrophysical objects whereshock waves are present. Stellar bow shocks, generated by runaway stars,have been previously detected in small numbers and well-studied. Alongwith progress in model development and improvements in observinginstruments, our knowledge of the emission produced by these objects andits origin can now be more clearly understood. Aims: We produce astellar bow-shock catalogue by applying uniform search criteria and asystematic search process. This catalogue is a starting point forstatistical studies, to help us address fundamental questions such as,for instance, the conditions under wich a stellar bow shock isdetectable. Methods: By using the newest infrared data releases,we carried out a search for bow shocks produced by early-type runawaystars. We first explored whether a set of known IRAS bow shockcandidates are visible in the most recently available IR data, which hasmuch higher resolution and sensitivity. We then carried out a selectionof runaway stars from the latest, large runaway catalogue available. Inthis first release, we focused on OB stars and searched for bow-shapedfeatures in the vicinity of these stars. Results: We provide abow-shock candidate survey that gathers a total of 28 members, which wecall the Extensive stellar BOw Shock Survey (E-BOSS). We derive the mainbow-shock parameters, and present some preliminary statistical resultson the detected objects. Conclusions: Our analysis of the initialsample and the newly detected objects yields a bow-shock detectabilityaround OB stars of ~10 per cent. The detections do not seem to dependparticularly on either stellar mass, age or position. The extension ofthe E-BOSS sample, with upcoming IR data, and by considering, forexample, other spectral types as well, will allow us to perform a moredetailed study of the findings.
| The Galactic O-Star Spectroscopic Survey. I. Classification System and Bright Northern Stars in the Blue-violet at R ~ 2500
We present the first installment of a massive spectroscopic survey ofGalactic O stars, based on new, high signal-to-noise ratio, R ~ 2500digital observations from both hemispheres selected from the GalacticO-Star Catalog of Maíz Apellániz et al. and Sota et al.The spectral classification system is rediscussed and a new atlas ispresented, which supersedes previous versions. Extensive sequences ofexceptional objects are given, including types Ofc, ON/OC, Onfp, Of?p,Oe, and double-lined spectroscopic binaries. The remaining normalspectra bring this first sample to 184 stars, which is close to completeto B = 8 and north of ? = -20° and includes all of thenorthern objects in Maíz Apellániz et al. that are stillclassified as O stars. The systematic and random accuracies of theseclassifications are substantially higher than previously attainable,because of the quality, quantity, and homogeneity of the data andanalysis procedures. These results will enhance subsequentinvestigations in Galactic astronomy and stellar astrophysics. In thefuture, we will publish the rest of the survey, beginning with a secondpaper that will include most of the southern stars in MaízApellániz et al.The spectroscopic data in this article were gathered with threefacilities: the 1.5 m telescope at the Observatorio de Sierra Nevada(OSN), the 3.5 m telescope at Calar Alto Observatory (CAHA), and the duPont 2.5 m telescope at Las Campanas Observatory (LCO). Some of thesupporting imaging data were obtained with the 2.2 m telescope at CAHAand the NASA/ESA Hubble Space Telescope (HST). The rest were retrievedfrom the DSS2 and Two Micron All Sky Survey (2MASS) surveys. The HSTdata were obtained at the Space Telescope Science Institute, which isoperated by the Association of Universities for Research in Astronomy,Inc., under NASA contract NAS 5-26555.
| uvby? photometry of early type open cluster and field stars
Context. The ? Cephei stars and slowly pulsating B (SPB) stars aremassive main sequence variables. The strength of their pulsationaldriving strongly depends on the opacity of iron-group elements. As manyof those stars naturally occur in young open clusters, whosemetallicities can be determined in several fundamental ways, it islogical to study the incidence of pulsation in several young openclusters. Aims: To provide the foundation for such aninvestigation, Strömgren-Crawford uvby? photometry of opencluster target stars was carried out to determine effectivetemperatures, luminosities, and therefore cluster memberships. Methods: In the course of three observing runs, uvby? photometryfor 168 target stars was acquired and transformed into the standardsystem by measurements of 117 standard stars. The list of target starsalso included some known cluster and field ? Cephei stars, as wellas ? Cephei and SPB candidates that are targets of theasteroseismic part of the Kepler satellite mission. Results: Theuvby? photometric results are presented. The data are shown to beon the standard system, and the properties of the target stars arediscussed: 140 of these are indeed OB stars, a total of 101 targets liewithin the ? Cephei and/or SPB star instability strips, and eachinvestigated cluster contains such potential pulsators. Conclusions: These measurements will be taken advantage of in a numberof subsequent publications.Based on measurements obtained at McDonald Observatory of the Universityof Texas at Austin.Tables 3-6 are only available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/528/A148
| A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun
Traditionally, runaway stars are O- and B-type stars with large peculiarvelocities. We would like to extend this definition to young stars (upto ?50 Myr) of any spectral type and to identify those present in theHipparcos catalogue by applying different selection criteria, such aspeculiar space velocities or peculiar one-dimensional velocities.Runaway stars are important for studying the evolution of multiple starsystems or star clusters, as well as for identifying the origins ofneutron stars. We compile the distances, proper motions, spectral types,luminosity classes, V magnitudes and B-V colours, and we utilizeevolutionary models from different authors to obtain star ages. We studya sample of 7663 young Hipparcos stars within 3 kpc from the Sun. Theradial velocities are obtained from the literature. We investigate thedistributions of the peculiar spatial velocity and the peculiar radialvelocity as well as the peculiar tangential velocity and itsone-dimensional components and we obtain runaway star probabilities foreach star in the sample. In addition, we look for stars that aresituated outside any OB association or OB cluster and the Galactic planeas well as stars for which the velocity vector points away from themedian velocity vector of neighbouring stars or the surrounding local OBassociation/cluster (although the absolute velocity might be small). Wefind a total of 2547 runaway star candidates (with a contamination ofnormal Population I stars of 20 per cent at most). Thus, aftersubtracting these 20 per cent, the runaway frequency among young starsis about 27 per cent. We compile a catalogue of runaway stars, which isavailable via VizieR.
| Masses and luminosities of O- and B-type stars and red supergiants
Massive stars are of interest as progenitors of supernovae, i.e.neutron stars and black holes, which can be sources of gravitationalwaves. Recent population synthesis models can predict neutron star andgravitational wave observations but deal with a fixed supernova rate oran assumed initial mass function for the population of massive stars. Here we investigate those massive stars, which are supernovaprogenitors, i.e. with O- and early B-type stars, and also allsupergiants within 3 kpc. We restrict our sample to those massive starsdetected both in 2MASS and observed by Hipparcos, i.e. only those starswith parallax and precise photometry. To determine the luminositieswe calculated the extinctions from published multi-colour photometry,spectral types, luminosity class, all corrected for multiplicity andrecently revised Hipparcos distances. We use luminosities andtemperatures to estimate the masses and ages of these stars usingdifferent models from different authors. Having estimated theluminosities of all our stars within 3 kpc, in particular for all O- andearly B-type stars, we have determined the median and mean luminositiesfor all spectral types for luminosity classes I, III, and V. Ourluminosity values for supergiants deviate from earlier results: Previouswork generally overestimates distances and luminosities compared to ourdata, this is likely due to Hipparcos parallaxes (generally moreaccurate and larger than previous ground-based data) and the fact thatmany massive stars have recently been resolved into multiples of lowermasses and luminosities. From luminosities and effective temperatureswe derived masses and ages using mass tracks and isochrones fromdifferent authors. From masses and ages we estimated lifetimes andderived a lower limit for the supernova rate of ?20 events/Myraveraged over the next 10 Myr within 600 pc from the sun. These data arethen used to search for areas in the sky with higher likelihood for asupernova or gravitational wave event (like OB associations).
| Broad-band optical polarimetric study of IC 1805
We present the BVR broad-band polarimetric observations of 51 starsbelonging to the young open cluster IC 1805. Along with the photometricdata from the literature, we have modelled and subtracted the foregrounddust contribution from the maximum polarization (Pmax) andcolour excess [E (B - V)]. The mean value of the Pmax forintracluster medium and the foreground are found to be 5.008 +/- 0.005and 4.865 +/- 0.022 per cent, respectively. Moreover, the mean value ofthe wavelength of maximum polarization (λmax) forintracluster medium is 0.541 +/- 0.003μ m, which is quite similar asthe general interstellar medium (ISM). The resulting intracluster dustcomponent is found to have negligible polarization efficiency ascompared to interstellar dust. Some of the observed stars in IC 1805have shown the indication of intrinsic polarization in theirmeasurements.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Early-type stars in the young open cluster IC 1805. II. The probably single stars HD 15570 and HD 15629, and the massive binary/triple system HD 15558
Aims.We address the issue of the multiplicity of the three brightestearly-type stars of the young open cluster IC 1805, namely HD 15570, HD15629 and HD 15558. Methods: .For the three stars, we measured theradial velocity by fitting Gaussian curves to line profiles in theoptical domain. In the case of the massive binary HD 15558, we also useda spectral disentangling method to separate the spectra of the primaryand of the secondary in order to derive the radial velocities of the twocomponents. These measurements were used to compute orbital solutionsfor HD 15558. Results: .For HD 15570 and HD 15629, the radialvelocities do not present any significant trend attributable to a binarymotion on time scales of a few days, nor from one year to the next. Inthe case of HD 15558 we obtained an improved SB1 orbital solution with aperiod of about 442 days, and we report for the first time on thedetection of the spectral signature of its secondary star. We derivespectral types O5.5III(f) and O7V for the primary and the secondary ofHD 15558. We tentatively compute a first SB2 orbital solution althoughthe radial velocities from the secondary star should be considered withcaution. The mass ratio is rather high, i.e. about 3, and leads to veryextreme minimum masses, in particular for the primary object. Minimummasses of the order of 150 ± 50 and 50 ± 15 M_ȯ arefound respectively for the primary and the secondary. Conclusions:.We propose that HD 15558 could be a triple system. This scenario couldhelp to reconcile the very large minimum mass derived for the primaryobject with its spectral type. In addition, considering new andpreviously published results, we find that the binary frequency amongO-stars in IC 1805 has a lower limit of 20%, and that previouslypublished values (80%) are probably overestimated.
| 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.
| 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.
| On the Absolute Magnitudes of the O Stars
The conclusion published in 1992 by Garmany & Stencel from a studyof northern OB associations, that the absolute magnitudes of the O starsshow ``a large scatter ... intrinsic to the classification system,'' iscritically examined. It is found that the differences between theirderived absolute magnitudes of O stars and this author's 1973calibration exhibit large systematic effects in several associations,ranging from -0.74 to +1.02 mag with substantially smaller dispersions.Of course, when these results are combined, the scatter equals the fullrange of the systematic effects. To investigate the possibility ofdistance errors, the Garmany & Stencel B0-B2.5 stars in the sameassociations are subjected to the same analysis. The results for the Bstars show no significant systematic differences, eliminating errors inthe association distances derived by Garmany & Stencel from the Bstars as the source of the differences found for the O stars. It isnoteworthy that the dispersions in the absolute magnitudes of the Bstars within a given association are similar to or larger than those ofthe O stars. An examination of the distribution on the sky of the starsshows that the O and B stars in the discrepant associations aregenerally not colocated; such was already known to be the case for theimportant Perseus OB1 association. It is suggested that despite theirefforts to improve them, significant problems remain with theassociation memberships adopted by Garmany & Stencel; the relativelysmall dispersions of the O star absolute magnitudes even in thediscrepant cases indicate that they belong to different, usually moredistant associations near the lines of sight to the B associations withwhich they have been mistakenly connected. Several individual cases ofunrecognized multiple systems and classification errors are also foundin the Garmany & Stencel sample. It is concluded that the scatter inthe absolute magnitudes of the O stars is not as large as found byGarmany & Stencel, and not larger than that of the B stars.
| Photometry and Classification of Stars Along the Camelopardalis and Perseus Border
Seven-color photometry in the Vilnius system for 309 stars down to 12.5mag in the area along the galactic equator near the Camelopardalis andPerseus border is presented. Photometric spectral and luminosity classesof the stars are determined.
| Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Spectroscopic observations of young open clusters: IC 1805, NGC 654 and NGC 6823
Spectroscopic observations were made for a sample of 263 stars fromthree young open clusters IC 1805, NGC 654 and NGC 6823 with CCDdetectors in the blue and yellow-red spectral regions. MKK types wereproperly determined for these stars by carefully comparing spectra ofprogram stars with those of a complete grid of MKK standards, which wereobserved with the same instruments as the program stars. For most of theobserved stars precise MKK types were assigned for the first time. A fewof early-type emission-line stars were discovered or confirmed. Thepresence of Be stars in the studied clusters is discussed. Spectra ofthe observed MKK standards also reveal lots of features showingtemperature or luminosity effect in the yellow-red region, which helpedin our stellar spectral classification.
| 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.
| A galactic chimney in the Perseus arm of the Milky Way
GALAXIES are surrounded by large haloes of hot gas1 whichmust be replenished as the gas cools. This has led to theconcept2 of galactic 'chimneys'-cavities in the interstellarmedium, created by multiple supernova explosions, that can act asconduits for the efficient transport of hot gas from a galaxy's disk toits halo. Here we present a high-resolution map of atomic hydrogen inthe Perseus arm of our Galaxy, which shows clear evidence for theexistence of such a chimney. This chimney appears to have been formed bythe energetic winds from a cluster of young massive stars, and maycurrently have reached the stage of blowing out into the halo.
| The Initial Mass Function and Massive Star Evolution in the OB Associations of the Northern Milky Way
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...454..151M&db_key=AST
| Intrinsic colour indices of O- and B- type stars in the Vilnius photometric system.
Not Available
| Interstellar extinction toward the CAS OB6 association: Where is the dust?
We have completed a multiband (ultraviolet, optical, and near-infrared)study of the interstellar extinction properties of nine massive stars inIC 1805 and IC 1848, which are both part of Cas OB6 in the Perseusspiral arm. Our analysis includes determination of absolute extinctionover the wavelength range from 3 micrometers to 1250 A. We haveattempted to distinguish between foreground dust and dust local to CasOB6. This is done by quantitatively comparing extinction laws of theleast reddened sightlines (sampling mostly foreground dust) versus themost reddened sightlines (sampling a larger fraction of the dust in theCas OB6 region). We have combined previous investigations to betterunderstand the evolution of the interstellar medium in this active starforming region. We found no variation of extinction curve behaviorbetween moderately reddend and heavily reddened Cas OB6 stars. None ofthe curves show any significant deviation from theCardelli-Clayton-Mathis (CCM) Rupsilon-dependent extinction.They are all consistent with that seen from diffuse dust. Most or all ofthe dust along the line of sight may be foreground to Cas OB6. Massivestar forming regions can show significant deviations from CCM behaviorwhich have been attributed to processing of the dust grains. Any dustlocal to the association must exist far from the hot stars in IC 1805and IC 1848. A previous episode of star formation may have alreadycleared out the region of most of the gas and dust. Evidence for thiscan be seen in H I and IRAS data of the region.
| 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.
| Photoelectric photometry of OB stars in the Vilnius system
Not Available
| Distribution and motions of OB stars in the direction of H and KHI Perseus.
Not Available
| Near-infrared photometric study of open star cluster IC 1805
The JHK magnitudes of 29 stars in the region of open star cluster IC1805 were measured. These, and the existing infrared and opticalobservations, indicate a normal interstellar extinction law in thedirection of the cluster. Further, most of the early-type stars havenear-infrared fluxes as expected from their spectral types. Patchydistribution of ionized gas and dust appears to be the cause ofnonuniform extinction across the cluster face.
| The upper main sequence of OB associations. II - The single-lined O stars: Spectral classification of northern stars and lines of C and N
The properties of the stars close to the upper main sequence of OBassociations are studied in order to provide constraints on the theoryof evolution of massive stars. The spectral classification of northernsingle-lined O stars, most of them belonging to the associations CygOB1, Per OB1 and Cas OB6, is presented. The classification is performedaccording to Conti's classification scheme for O stars, amended byMathys (1988). The behavior of the C and N lines of the stars isstudied, in order to determine whether CNO-processed material is visibleat their surface. Three new ON stars have been discovered: BD + 36 deg4063 (O9.71), HD 13268 (O8V), and HD 110360 (O7V).
| Reddening and polarimetric studies toward IC 1805
Near IR and (V-I) photometry is presented for probable members in thecluster IC 1805. From a color-difference analysis, the ratio of total toselective absorption R(v), is found to be uniform across the cluster andcalculated to be 3.1 + or - 0.1. Assuming a distance modulus to theHyades of 3.3 mag, a distance to IC 1805 of 2.4 + or - 0.1 kpc isobtained by employing several ZAMS fitting calibrations. The resultantC-M diagram contains both MS and ZAMS B type stars, implying thatmassive star formation in the cluster was a continuous process.Photometric and spectroscopic data for foreground stars toward thecluster indicate that at least two-thirds of the reddening of thecluster is due to the general interstellar material (IM). Multicolorpolarimetric measurements are also presented for 24 probable clustermembers and for 49 foreground objects. It is concluded that the visualpolarization across the local galactic spiral arm is 5 percent, and thatthe size distribution of grains within IC 1805 is similar to that in theforeground region. After correcting for foreground IM, the residualintracluster polarization indicates that the cluster may be located neara Parker (1966) magnetic well with field strength similar to that of theforeground IM.
| The Einstein X-ray Observatory Catalog of O-type stars
A catalog of X-ray count rates for all O-type stars surveyed by theEinstein Observatory is presented. The procedures by which the IPC andHigh Resolution Imager rates are converted to emitted X-ray luminositiesare discussed in detail. The catalog contains 289 stars with 89detections and 176 upper bounds for the observed count rates. Precisepositions for 43 O-type stars are given whose previously known locationswere unknown or erroneous. It is argued that most O-type stars are X-raypoint sources, but some are possibly embedded in extended nebulae and/orbubbles. The X-ray spectra of O-type stars are discussed briefly, and itis argued that their mean spectrum can reasonably be taken as an 0.5 keVthermal bremsstrahlung model. It is argued that at least 30 percent ofall O-type stars are variable in X-rays.
| H-alpha as a tracer of mass loss from OB stars
This paper investigates the use of the H-alpha emission from stellarwinds of OB stars to determine the stellar mass-loss rate. The power inH-alpha emitted by the wind can be parameterized in terms of thetemperature and the density field of the wind. A simple expression isderived which relates the observed H-alpha luminosity to the stellarmass-loss rate, the stellar radius, the velocity law, and the stellareffective temperature. This expression is calibrated for the influenceof the velocity law using a sample of Galactic OB stars with UVmass-loss rates. Consequently, the results depend on the validity of theUV rates. The derived velocity law for O stars turns out to be inagreement with the radiation-pressure-driven wind theory. There isevidence for a dependence of the velocity-law gradient on spectral type.The results for B stars, however, are more uncertain due to thedependence on the adopted mass accretion rate/L relation. Application ofthe calibrated H-alpha luminosity/mass-loss rate relation to a sample of149 galactic OB stars shows that mass accretion rate can be reliablydetermined from H-alpha. Due to the moderate amount of observing timerequired to derive mass accretion rate from H-alpha, this method may beapplied successfully to investigate mass-loss effects in extra-Galacticstars.
| Mass to line-strength relations from IUE spectra of early-type stars
An extensive survey of the 1200-1900 A region in OB type stellar spectraobtained from the IUE archives has been used to establish line-strengthversus spectral-type relationships. One hundred and sixty-threelow-resolution IUE spectra of 124 well-classified O3 to B5 stars wereexamined. Earlier results that the equivalent width of Si IV (1400 A)and C IV (1550 A) features are well correlated with optical spectraltype are confirmed. The equivalent width/spectral type/luminosity classrelations for these features are then established.
| Galactic cluster star radial velocities obtained with a focal reducer field spectrograph. I - The clusters IC 1805, NGC 2287, NGC 2548, IC 4665, NGC 6633, NGC 6940 and NGC 7092
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985A&AS...62..301G&db_key=AST
| Catalog of BV magnitudes and spectral classes of 6000 stars
The present catalog, compiled at the Abastumani Observatory, contains BVmagnitudes and spectral classes of about 6000 stars up to V(lim) = 13.0min five circular areas of 18 sq deg located near the salactic-equatorplane. The catalog is intended for star-statistics studies ofstar-formation regions.
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