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The conspicuous absence of X-ray emission from carbon-enriched Wolf-Rayet stars
The carbon-rich WC5 star WR 114 was not detected during a 15.9 ksecXMM-Newton, observation, implying an upper limit to the X-ray luminosityof LX < 2.5x 1030 erg s-1 andto the X-ray to bolometric luminosity ratio ofLX/Lbol < 4*E-9. This confirmsindications from earlier less sensitive measurements that there has beenno convincing X-ray detection of any single WC star. This lack ofdetections is reinforced by XMM-Newton, and CHANDRA observations of WCstars. Thus the conclusion has to be drawn that the stars withradiatively-driven stellar winds of this particular class areinsignificant X-ray sources. We attribute this to photoelectronicabsorption by the stellar wind. The high opacity of the metal-rich anddense winds from WC stars puts the radius of optical depth unity athundreds or thousands of stellar radii for much of the X-ray band. Webelieve that the essential absence of hot plasma so far out in the windexacerbated by the large distances and correspondingly high ISM columndensities makes the WC stars too faint to be detectable with currenttechnology. The result also applies to many WC stars in binary systems,of which only about 20% are identified X-ray sources, presumably due tocolliding winds.
| Wolf-Rayet star parameters from spectral analyses
The Potsdam non-LTE code for expanding atmospheres, which accounts forclumping and iron-line blanketing, has been used to establish a grid ofmodel atmospheres for WC stars. A parameter degeneracy is discovered forearly-type WC models which do not depend on the `stellar temperature'.15 Galactic WC4-7 stars are analyzed, showing a very uniform carbonabundance (He:C = 55:40) with only few exceptions.
| The Effect of Binarity and Metallicity in the Spectra of WC and WO Stars
A statistical analysis of the main emission lines common to the WC andWO stars is made based on an extensive set of spectral data. To definethe trends in equivalent width ( Wλ), line ratios, andline widths, median values are derived for single-spectrum stars ofdifferent spectral class. We find that in Galactic WO and WC4 stars,Wλ (C IV 581 nm) is smaller compared to inextragalactic objects. In both Galactic and extragalactic stars,Wλ (O V 559 nm) smoothly increases towards early WCand WO stars. It is argued that differences in stellar wind structure,in combination with the ambient metallicity, may be the cause of theanomalies. Variation of the profile of the 465 nm blend indicates asubstantial contribution of He II 468 nm for the WCE and WO stars. Inaddition, we comment on the carbon abundances in relation to theevolutionary status of these objects. We also give an estimate of theOB/WR continuum flux ratio in composite-spectrum systems.
| Kinematical Structure of Wolf-Rayet Winds. I.Terminal Wind Velocity
New terminal wind velocities for 164 Wolf-Rayet stars (from the Galaxyand LMC) based on PCyg profiles of lambda1550 CIV resonance line werederived from the archive high and low resolution IUE spectra availableform the INES database. The high resolution data on 59 WR stars (39 fromthe Galaxy and 20 from LMC) were used to calibrate the empiricalrelation lambda_min^Abs- lambda_peak^Emis vs terminal wind velocity,which was then used for determinations of the terminal wind velocitiesfrom the low resolution IUE data. We almost doubled the previous mostextended sample of such measurements. Our new measurements, based onhigh resolution data, are precise within 5-7%. Measurements, based onthe low resolution spectra have the formal errors of approx 40-60%. Acomparison of the present results with other determinations suggestshigher precision of approx 20%. We found that the terminal windvelocities for the Galactic WC and WN stars correlate with the WRspectral subtype. We also found that the LMC WN stars have winds slowerthan their Galactic counterparts, up to two times in the case of the WNEstars. No influence of binarity on terminal wind velocities was found.Our extended set of measurements allowed us to test application of theradiation driven wind theory to the WR stars. We found that, contrary toOB stars, terminal wind velocities of the WR stars correlate only weaklywith stellar temperature. We also note that the terminal to escapevelocity ratio for the WR stars is relatively low: 2.55 pm 1.14 for theGalactic WN stars and 1.78 pm 0.70 for the Galactic WCs. This ratiodecreases with temperature of WR stars, contrary to what is observed inthe case of OB stars. The presented results show complex influence ofchemical composition on the WR winds driving mechanism efficiency. Ourkinematical data on WR winds suggest evolutionary sequence: WNL -->WNE --> WCE --> WCL.
| First Detections of Molecular Gas Associated with the Wolf-Rayet Ring Nebula NGC 3199
This paper presents the first observations of molecular gas associatedwith the Wolf-Rayet ring nebula NGC 3199 around the WR star WR 18. Thisincludes first observations of the molecules HCN, HCO+, CN,and HNC seen in any Wolf-Rayet ring nebula. Our observations immediatelysuggest the presence of high-density molecular gas (>104cm-3) in the nebula with significant amounts of associatedmolecular gas, which is in the form of clumpy ejecta and/or interstellarmaterial. Molecular CO gas was mapped across the optically brightportion of the nebula and out into the diffuse ionized component usingthe 12CO J=1-->0 line. CO gas is not seen within theoptically bright rim of NGC 3199 but adjacent to it. The opticalemission rim therefore appears to mark regions of photodissociation.Velocity components in the CO data are consistent with those seen inhigh-resolution optical spectra of the Hα line but extend beyondthe visible emission. A prior suggestion of the formation of the nebulavia a bow shock appears unlikely since Hipparcos measurements show theproper motion of WR 18 is almost at right angles to the directionrequired for the bow shock model. Instead, line splitting toward thenorth of the nebula suggests that a possible blowout of the Wolf-Rayetwind through surrounding ejecta may be responsible for some of thevelocity features observed. Preliminary estimates of molecularabundances in the nebula seen toward the central star are significantlyhigher than for the interstellar medium and are similar to those inplanetary nebulae, although CN is distinctly underabundant in comparisonto the very high values found in many planetary nebulae. The abundancesfound are consistent with the idea that at least a portion of themolecular material is associated with ejecta from the central star.Based on observations collected at the Swedish-ESO SubmillimetreTelescope (SEST) at the European Southern Observatory, La Silla, Chile.The Swedish-ESO Submillimetre Telescope is operated jointly by theEuropean Southern Observatory (ESO) and the Swedish National Facilityfor Radio Astronomy, Onsala Space Observatory, at Chalmers University ofTechnology.
| The VIIth catalogue of galactic Wolf-Rayet stars
The VIIth catalogue of galactic PopulationI Wolf-Rayet stars providesimproved coordinates, spectral types and /bv photometry of known WRstars and adds 71 new WR stars to the previous WR catalogue. This censusof galactic WR stars reaches 227 stars, comprising 127 WN stars, 87 WCstars, 10 WN/WC stars and 3 WO stars. This includes 15 WNL and 11 WCLstars within 30 pc of the Galactic Center. We compile and discuss WRspectral classification, variability, periodicity, binarity, terminalwind velocities, correlation with open clusters and OB associations, andcorrelation with Hi bubbles, Hii regions and ring nebulae. Intrinsiccolours and absolute visual magnitudes per subtype are re-assessed for are-determination of optical photometric distances and galacticdistribution of WR stars. In the solar neighbourhood we find projectedon the galactic plane a surface density of 3.3 WR stars perkpc2, with a WC/WN number ratio of 1.5, and a WR binaryfrequency (including probable binaries) of 39%. The galactocentricdistance (RWR) distribution per subtype shows RWRincreasing with decreasing WR subtype, both for the WN and WC subtypes.This RWR distribution allows for the possibility ofWNE-->WCE and WNL-->WCL subtype evolution.
| Exospheric models for the X-ray emission from single Wolf-Rayet stars
We review existing ROSAT detections of single Galactic Wolf-Rayet (WR)stars and develop wind models to interpret the X-ray emission. The ROSATdata, consisting of bandpass detections from the ROSAT All-Sky Survey(RASS) and some pointed observations, exhibit no correlations of the WRX-ray luminosity (LX) with any star or wind parameters ofinterest (e.g. bolometric luminosity, mass-loss rate or wind kineticenergy), although the dispersion in the measurements is quite large. Thelack of correlation between X-ray luminosity and wind parameters amongthe WR stars is unlike that of their progenitors, the O stars, whichshow trends with such parameters. In this paper we seek to (i) test byhow much the X-ray properties of the WR stars differ from the O starsand (ii) place limits on the temperature TX and fillingfactor fX of the X-ray-emitting gas in the WR winds. Adoptingempirically derived relationships for TX and fXfrom O-star winds, the predicted X-ray emission from WR stars is muchsmaller than observed with ROSAT. Abandoning the TX relationfrom O stars, we maximize the cooling from a single-temperature hot gasto derive lower limits for the filling factors in WR winds. Althoughthese filling factors are consistently found to be an order of magnitudegreater than those for O stars, we find that the data are consistent(albeit the data are noisy) with a trend of fx ∝(Mν&infy;)-1 in WR stars, as is also the casefor O stars.
| 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.
| Wolf-Rayet stars and O-star runaways with HIPPARCOS. I. Kinematics
Reliable systemic radial velocities are almost impossible to secure forWolf-Rayet stars, difficult for O stars. Therefore, to study the motions- both systematic in the Galaxy and peculiar - of these two relatedtypes of hot, luminous star, we have examined the Hipparcos propermotions of some 70 stars of each type. We find that (a) both groupsfollow Galactic rotation in the same way, (b) both have a similarfraction of ``runaways'', (c) mean kinetic ages based on displacementand motion away from the Galactic plane tend to slightly favour thecluster ejection over the the binary supernova hypothesis for theirformation, and (d) those with significant peculiar supersonic motionrelative to the ambient ISM, tend to form bow shocks in the direction ofthe motion. Based on data from the ESA Hipparcos astrometry satellite.Table~1 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Large IRAS Shells Around Galactic Wolf-Rayet Stars and the O Star Phase of Wolf-Rayet Evolution
Abstract image available at:http://adsabs.harvard.edu/abs/1996AJ....112.2828M
| X-ray and γ-ray emission in open clusters.
We have studied a number of galactic open clusters that lie in the errorboxes of COS B sources. These clusters belong to complexes in whichsimilar star formation processes occur. They have similar ages, stellarpopulation and contain peculiar stars with very high-velocity stellarwinds. We propose that a system of shock fronts, set up at theinterfaces between the hypersonic wind of the peculiar stars and theother cluster members, generates acceleration of cosmic ray particles,whose interactions with the inter-cluster gas concentrations would beresponsible for the observed γ-ray emission. We find variousobservational evidences (including CGRO data, strongly supporting theassociation of the γ-ray source J 2021+37=2CG075+00 with Berk 87)for the presence of such shock fronts in some of these clusters. We showthat the diffuse hard X-ray emission from the clusters regions isconsistent with the geometric scenario inferred from the data and withthe assumed mechanism of cosmic ray acceleration.
| An IRAS-based Search for New Dusty Late-Type WC Wolf-Rayet Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJS..100..413C&db_key=AST
| Spectral analyses of 25 Galactic Wolf-Rayet stars of the carbon sequence.
We present a grid of helium-carbon models for Wolf-Rayet (WR) stars ofthe carbon sequence (WC) with β_ C_=0.2 (carbon mass fraction),thus extending our previously released grid with β_C_=0.6 to adifferent chemical composition. The WR model atmospheres are based onthe so-called standard assumptions. The calculations account for non-LTEradiation transfer in spherically expanding atmospheres. Helium andcarbon are represented by detailed model atoms, especially concerningthe ions Ciii and Civ. Using the model grids 25 Galactic WC stars ofintermediate subtype (WC5 to WC8) are analyzed. Subsequently we performfine analyses by calculating several individual models for each of theprogram stars. Temperatures, radii, mass-loss rates and terminalvelocities are determined together with the carbon to helium ratio. Theanalyzed WC stars are found to form two groups, which can bedistinguished by the strength of their emission lines. Stars with weaklines (WC-w) have effective temperatures close to 50kK and their windsare relatively thin, forming the continuous spectrum in regions withsmall expansion velocities. WC stars with strong lines (WC-s) havehigher effective temperatures (60 to 100kK, referring to the coreradius) and thick winds. Thus there is a strong analogy to thedistribution of the early-type WN stars (WNE-w and WNE-s, respectively).For the WC stars we determine luminosities between 10^4.7^ and10^5.5^Lsun_ and mass-loss rates from 10^-4.8^ to10^-3.9^Mȯ/yr. The carbon mass fraction varies from 0.2 to 0.6. Nocorrelation is found between the carbon abundance and any of the stellarparameters (e.g. temperature, luminosity) or the spectral subtype. Theevolution of WR stars is discussed by comparing the results of ouranalyses with evolutionary tracks.
| A Large Bubble External to the Wolf-Rayet Ring Nebula NGC 6888
Abstract image available at:http://adsabs.harvard.edu/abs/1995AJ....109.2257M
| 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.
| Terminal Velocities of Wolf-Rayet Star Winds from Low Resolution IUE Spectra
Attracted by the simplicity of the recently published by Prinja (1994)method of determination of terminal wind velocities in hot stars fromlow resolution IUE spectra we investigate its application to WR stars.With a large sample of low resolution IUE spectra of WR stars we foundeven simpler, that is linear instead of square, empirical relationbetween Delta lambda as defined by Prinja (1994) and terminal windvelocity -- vinfty. Using this new empirical relation wepresent vinfty for a sample of 85 galactic and LMC stars, 19of them determined for the first time. We almost tripled the number ofterminal velocity determinations for LMC WR stars. The comparison withother determinations shows that this simple method is accurate to within10-20%. We confirm the correlation between terminal velocity and WCsubtype. We also show that terminal velocities of WN stars are lowerthan that of WCE. A comparison between galactic and LMC stars shows thatthe LMC WN stars have slower winds in most of WN subtypes.
| The ROSAT PSPC survey of the Wolf-Rayet stars
Not Available
| Low resolution IUE spectra of Wolf-Rayet stars.
We present uniformly reduced and measured equivalent widths, FWHM andobserved line fluxes for 94 "single" WR stars (34 galactic WN, 22galactic WC, 31 LMC WN and 7 LMC WC) based on the archive IUE spectra ofWR stars gathered from different observational runs and from differentepochs. The spectra are used for spectral classification in theultraviolet region and for searching correlations among the strength andwidths of emission lines of different ions. Some correlations withoptical and near IR lines observed by other authors are given as well.The set of spectra we use is almost complete to 12 magnitude andrepresentative according to spectral subtype of WR stars.
| A survey of nebulae around galactic wolf-rayet stars in the southern sky, 2.
We present the second half of a charge coupled device (CCD) narrow-bandimaging survey of galactic Wolf-Rayet stars located in the southernhemisphere as listed by van der Hucht et al. (1981). Images of 50Wolf-Rayet stars were taken using a wide-field CCD and narrowbandinterference filters centered on H alpha and (O III) 5007 A wavelengths.The first half of the survey (Marston, Chu, & Garcia-Segura 1993,hereafter Paper I) revealed six new ring nebulae residing aroundWolf-Rayet stars. Here we reveal a possible 11 new rings and theexistence of multiple rings associated with two previously known nebula,RCW 118 and G2.4+1.4 and around the stars WR 16 and WR 43. Combining ourresults with those of Miller & Chu (1993) and Paper I, 92% of thevan der Hucht catalog of Wolf-Rayet stars have now been surveyed. Of the38 possible ring nebulae found in our surveys to date, 22 reside aroundWN subtype Wolf-Rayet stars, 13 around WC stars, one around a triplet ofWolf-Rayet stars and one around a WO star (WR 102). One ring existsaround a WN/WC star (WR 98). A bias toward rings being observed aroundW-R + OB binaries is noted. Such pairings are generally bright, and thedetection of a ring around them may merely be a function of theircombined luminosity. Several Wolf-Rayet stars are shown to be surroundedby multiple rings (two or three) which suggests that a number ofejections of stellar material have taken place during their evolution.
| Spectrophotometry of Wolf-Rayet stars. I - Continuum energy distributions
All available low-resolution IUE spectra are assembled for Galactic,LMC, and SMC W-R stars and are merged with ground-based optical and NIRspectra in order to collate in a systematic fashion the shapes of theseenergy distributions over the wavelength range 0.1-1 micron. They can beconsistently fitted by a power law of the form F(lambda) isapproximately equal to lambda exp -alpha over the range 1500-9000 A toderive color excesses E(B-V) and spectral indices by removing the 2175-Ainterstellar absorption feature. The WN star color excesses derived arefound to be in good agreement with those of Schmutz and Vacca (1991) andKoesterke et al. (1991). Significant heterogeneity in spectral indexvalues was generally seen with any given subtype, but the groupsconsisting of the combined set of Galactic and LMC W-R stars, theseparate WN and WC sequences, and the Galactic and LMC W-R stars allshowed a striking and consistent Gaussian-like frequency distribution ofvalues.
| Search for second-phase Wolf-Rayet binaries among WRE stars
Previous searches of WR + c binaries have concentrated on thenarrow-line WRL stars, whose radial velocities (RV) and hence orbits canin principle be measured more precisely than for broad-line WRE stars.This investigation extends the search for WR + c systems to WRE stars,which are expected to have larger RV amplitudes because of their smallermasses compared to WRL stars. Negative RV results for 2 WCE and 2 WNEstars presented here, combined with previous searches, are mildly atodds with the number of second-phase WR binaries expected (about 15-20percent) among a random sample of Galactic solar-neighborhood WR stars.Among the 51 WR stars brighter than v = 11 mag, the best WR + ccandidates are still EZ CMa and possibly HD 197406, although even theseare not compelling.
| Search for H I bubbles around Wolf-Rayet stars between L = 302 deg and 312 deg
The results of a search for H I bubbles around the 14 WR stars known inthe section of the Galaxy between l = 302 deg and l = 312 deg arepresented. The results disclose four additional H I bubbles, all aroundWR stars at Galactic latitudes higher than absolute value of b = 2 deg.This increases to eight the number of known neutral gas bubblessurrounding WR stars. The new H I voids are associated with the WR stars52, 54, 57, and 61. The fact that no H I bubbles were found around WRstars close to the Galactic midplane is probably a selection effect.
| Color excesses, intrinsic colors, and absolute magnitudes of Galactic and Large Magellanic Cloud Wolf-Rayet stars
A new method of determining the color excesses of WR stars in the Galaxyand the LMC has been developed and is used to determine the excesses for44 Galactic and 32 LMC WR stars. The excesses are combined withline-free, narrow-band spectrophotometry to derive intrinsic colors ofthe WR stars of nearly all spectral subtypes. No correlation of UVspectral index or intrinsic colors with spectral subtype is found forthe samples of single WN or WC stars. There is evidence that early WNstars in the LMC have flatter UV continua and redder intrinsic colorsthan early WN stars in the Galaxy. No separation is found between thevalues derived for Galactic WC stars and those obtained for LMC WCstars. The intrinsic colors are compared with those calculated frommodel atmospheres of WR stars and generally good agreement is found.Absolute magnitudes are derived for WR stars in the LMC and for thoseGalactic WR stars located in clusters and associations for which thereare reliable distance estimates.
| The distribution of massive stars in the Galaxy. I - The Wolf-Rayet stars
Using spectroscopic parallax, the heliocentric and Galactocentricdistances of nearly all of the 157 known Wolf-Rayet stars in the Galaxywere determined. Their distribution both within and perpendicular to theGalactic plane was investigated. The overall distribution within theplane reveals spiral features which are in accord with otherdeterminations of Galactic structure. In addition, it was found that theGalactocentric location of Wolf-Rayet stars is dependent on Wolf-Rayetsubtype, with late WC stars strongly confined to regions within thesolar circle. However, there is only a marginal variation in the WC/WNnumber ratio with distance from the Galactic center. The distribution ofWolf-Rayet stars in the direction perpendicular to the plane revealsthat these objects are closely confined to, but distributedasymmetrically about, the Galactic plane; the verical scale height ofthe distribution is about 45 pc. It is found that the sun is locatedabout 15 pc above the plane defined by these extreme Population Iobjects.
| Distances of Galactic WC stars from emission-line fluxes and a quantification of the WC classification
The extent to which later-type WC stars in the Galaxy show constant fluxin the carbon lines is assessed. It is found the the WC stars are anextremely 'well-behaved' sequence in terms of quantitative spectroscopicproperties. The two classification parameters are closely correlatedwith a scatter of the order of uncertainty. There appear to be naturalbreaks in the sequence between subclasses, except between WC5 and 6. Theclassification is quantified using the C IV 5808 A/C III 5696 A ratio asthe principal defining parameter for WC7-9 stars and the C III 5696 A/OV 5590 A ratio as the principal defining parameter for WC4-6 stars.Preliminary calibration of the line fluxes indicate that the flux of CIV 5808 A in Galactic WC stars is constant at F(0) 5808 = -logF(0)(5808) = 8.1 at 1 kpc for subclasses WC5-7. The intrinsic line fluxratio C(0) = log f(0)(5808/4650) is a smooth function of subclassnumber, decreasing from -0.22 dex for WC4 stars to -0.56 dex for WC9stars.
| Spectroscopic studies of Wolf-Rayet stars. VI - Optical spectrophotometry of near-infrared emission lines in some Galactic stars
Spectroscopy of 47 WN stars and 36 WC stars in the Galaxy in thenear-infrared is presented. In the WN types, the strongest lines are dueto He II transitions and N IV at the 7115 A. In WC types, the strongestlines are due to C III, particularly at 9711 A; C II transitions, thestrongest at 7236 A, and C IV lines, particularly at 7726 A, are alsofound. It is a relatively easy procedure to determine the W-R class fromthis wavelength region; similarly, the distinction between WNE ('early')and WNL ('late'), and between WCE ('early') and WCL ('late') may also bemade, although numerical W-R subtypes cannot easily be determined fromthis near-infrared region. A comparison of line ratios of the variousions found in W-R stars suggests that it is only the optical N IV 4057 Aand C III 5696 A transitions which do not behave in a 'well-understood'manner; curiously enough, it is just these lines that play an importantrole in the traditional numerical subtype definitions.
| WR stars with the O VI 3811, 3834 A emission doublet. I - The catalog of the WR-O VI stars and spectroscopic studies of the WR-O VI stars HD 16523, HD 17638, and HD 192103
The catalog of the classical WR stars which have the emission doubletOvi 223811, 3834 in their optical spectra (the catalog of the WR-Ovistars) and the results of the spectroscopic investigations of the WR-Ovistars HD 16523, HD 17638, and HD 192103 are presented. Rapid spectralvariability of the emission doublet Ovi 223811, 3834 in the spectra ofWR-OvI stars HD 16523, HD 17638, and of the emission band 223680-3780 Ain the spectra of the WR-Ovi star HD 16523 is observed. It is shown thatspectral sub-types of the stars HD 16523 and HD 17638 as estimated fromdifferent criteria are uncertain. We argue that the WR-Ovi stars HD16523 and HD 17638, the optical spectra of which display emissiondoublet Ovi 223811, 3834, may be considered as W05 stars. The sub-typeW05 is proposed for the first time. Classification criteria of the W05sub-type are represented. The possible contribution of the ions HeII tothe emission at 23811 A and 23834 A is investigated. The z-distributionsof WR-O vi stars and WR stars with the probable relativistic companionsare found to be similar
| Intensive photometry of southern Wolf-Rayet stars
Results of an intensive photometric campaign on 17 of the brightestsouthern Wolf-Rayet stars are presented. The detection ofmultiperiodicity in two stars, HD 50896 and HD 96548, is reported. It islikely that these periodicities are not coherent but are manifestationsof the quasi-periodic variations seen in a few WR stars. A good exampleof these variations is given by HD 86161. A new eclipsing binary, HD92740, has been discovered; other stars show periodic variations whichcan be explained by phase-dependent scattering of the secondary light asit traverses the Wolf-Rayet wind. An important conclusion of this studyis that not a single example was found of short-period variations whichcan be attributed to pulsation.
| Photometry of southern Wolf-rayet stars.
Not Available
| The H I bubble around the Wolf-Rayet star HD 156385 and its environs
Based upon a study of the distribution of the interstellar H I21-cm-line emission around the Wolf Rayet star HD 156385, the presenceof a remarkable expanding H I bubble, radio-counterpart of the opticalnebula RCW 114, has been discovered which is surrounded by a thick H Ishell. Both the H I and optical features display outstandingly similarmorphologies, and have been created by the action of the strong stellarwind of the WR star and its massive progenitor. The H I bubble has aradius of 57 pc, an expansion velocity of 10 km/s, and a swept-up H Imass of 6300 solar masses.
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