Detection of the radial velocity curve of the B5-A0 supergiant companion star of Cir X-1?
In this paper, we report on phase-resolved I-band optical spectroscopicand photometric observations of Cir X-1 obtained with the Very LargeTelescope. The spectra are dominated by Paschen absorption lines atnearly all orbital phases except near phase zero (coinciding with theX-ray dip) when the absorption lines are filled in by broad Paschenemission lines. The radial velocity curve of the absorption linescorresponds to an eccentric orbit (e = 0.45) whose period and time ofperiastron passage are consistent with the period and phase predicted bythe most recent X-ray dip ephemeris. We found that the I-band magnitudedecreases from 17.6 to ~16.8 near phase 0.9-1.0 this brighteningcoincides in phase with the X-ray dip. Even though it is likely that theabsorption-line spectrum is associated with the companion star of CirX-1, we cannot exclude the possibility that the spectrum originates inthe accretion disc. However, if the spectrum belongs to the companionstar, it must be a supergiant of spectral type B5-A0. If we assume thatthe compact object does not move through the companion star atperiastron, the companion star mass is constrained to <~10Msolar for a 1.4-Msolar neutron star, whereas theinclination has to be . Alternatively, the measured absorption lines andtheir radial velocity curve can be associated with the accretion discsurrounding a 1.4-Msolar neutron star and its motion aroundthe centre of mass. An absorption-line spectrum from an accretion discis typically found when our line of sight passes through the accretiondisc rim implying a high inclination. In this scenario, the companionstar mass is found to be ~0.4 Msolar. However, from radioobservations it was found that the angle between the line of sight andthe jet axis is smaller than 5°. This would mean that the jetploughs through the accretion disc in this scenario, making thissolution less probable.
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Light variations of alpha Cygni variables in the Magellanic Clouds
We present time-series monitoring of 19 Magellanic Cloud super- andhypergiants, among which 13 alpha Cygni variables, viz.: S18 =AzV154, HDE268835 = R66, HD37974 = R126, HDE268757 = R59, HDE268822 =GV505, HDE269355 = GV258, HDE269612 = GV322, HDE270025 = GV439, AzV121,HD5277 = AzV136 = R10, AzV197, AzV310 = R26, and AzV369; the LMC starsHD32034 = GV80 = R62, HDE268819 = GV91, HDE269661 = GV346 = R111,HDE269697 = GV352, HDE269953 = GV423 = R150 and HDE270111 = GV460.
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A photometric study of 11 massive stars in the Magellanic Clouds
We present and discuss VBLUW photometry of eleven massive stars in theMagellanic Clouds: the SMC stars AzV 121, AzV 136 = HD 5277 = R 10, AzV197, AzV 310 = R 26 and AzV 369; the LMC stars GV 80 = HD 32034 = R 62,GV 91 = HDE 268 819, GV 346 = HDE 269661 = R 111, GV 352 = HDE 269697,GV 423 = HDE 269953 = R 150 and GV 460 = HDE 270111. Only one G0 Ia SMCsupergiant is found to be variable, whereas all members of the LMCsample show definite variability. We find that roughly aboveM/M\sun = 25, supergiants become photometrically unstable.The reddening-independent metal-index [B-L] is used to investigate themetallicity of the late-type supergiants in both galaxies relative tosimilar supergiants in the solar neighbourhood.
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STELIB: A library of stellar spectra at R ~ 2000
We present STELIB, a new spectroscopic stellar library, available athttp://webast.ast.obs-mip.fr/stelib. STELIB consists of an homogeneouslibrary of 249 stellar spectra in the visible range (3200 to 9500Å), with an intermediate spectral resolution (la 3 Å) andsampling (1 Å). This library includes stars of various spectraltypes and luminosity classes, spanning a relatively wide range inmetallicity. The spectral resolution, wavelength and spectral typecoverage of this library represents a substantial improvement overprevious libraries used in population synthesis models. The overallabsolute photometric uncertainty is 3%.Based on observations collected with the Jacobus Kaptein Telescope,(owned and operated jointly by the Particle Physics and AstronomyResearch Council of the UK, The Nederlandse Organisatie voorWetenschappelijk Onderzoek of The Netherlands and the Instituto deAstrofísica de Canarias of Spain and located in the SpanishObservatorio del Roque de Los Muchachos on La Palma which is operated bythe Instituto de AstrofÃsica de Canarias), the 2.3 mtelescope of the Australian National University at Siding Spring,Australia, and the VLT-UT1 Antu Telescope (ESO).Tables \ref{cat1} to \ref{cat6} and \ref{antab1} to A.7 are onlyavailable in electronic form at http://www.edpsciences.org. The StellarLibrary STELIB library is also available at the CDS, via anonymous ftpto cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/402/433
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Red supergiants in the LMC - IV: Calibration of intrinsic colours and the HRD
A new calibration of the (B-V)0, (V-R)0 and(V-I)0 colours in the Kron-Cousins system for F to Msupergiants and of the (V-K)0 colours in the SAAO system of Kto M supergiants in the LMC as measures of effective temperature andbolometric correction is given. For F to G supergiants the theoreticalTeff-intrinsic colour- relations given by Lejeune et al.(1997) on the basis of their own model atmospheres agree mostly wellwith our observations. For K to M supergiants, however, their intrinsiccolours are too red in most cases. The relations given by Bessell et al.(1998) based on the model atmospheres of Plez (1997) fit theobservations better, but their synthetic colours are often also too red.The calibration of the bolometric correction is not reproduced well byany of the models. The HRD of the stars shows two distinct groups, onewith log Teff above 3.80 and one with log Teffbetween 3.53 and 3.62. The upper luminosity and therefore the mass limitdepends significantly on effective temperature. The F to G stars haveMbol up to -9.8 mag (corresponding to 45 Msun),while the K to M stars do not exceed - -9.0 mag (corresponding to 31Msun). Neither the Geneva nor the Padova models can fit thepositions of the most luminous and the coolest supergiants. Thediscrepancy between theory and observation increases both withincreasing mass loss rate and overshooting. Best agreement with theobservations is reached by assuming mass loss rates of 2/3 of the deJager et al. (1988) mass loss rates. As shown both by the luminosity andinitial mass function, very luminous (i.e. massive) stars areoverproportionally rare. With -3.73 +/- 0.20 the slope of the initialmass function is very steep in the considered range of 16-35Msun, but confirms the results obtained by Massey et al.(1995) from an extensive study of the field OB stars both in theMagellanic Clouds and the Galaxy.
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Red supergiants in the LMC - III: luminous F and G stars
New BVRI observations for 40 and spectrophotometric measurements for 23F to G LMC supergiant candidates (and 3 galactic F to G supergiants) arepresented. The errors of the BVRI data are 0.01 to 0.03 mag in mostcases. The wavelength range of the spectra is 3400 to 6400 Angstroms,their resolution 10 Angstroms. The mean error of the fluxes is 0.03 mag.Spectral indices measuring the strengths of the Hβ , Hγ ,Hdelta , NaD and CaII H+K lines, the CHα_ {0} and CNbeta_ {0}bands, of the Balmer jump and the slope of the continuum redwards arediscussed as measures of effective temperature and luminosity on thebasis of galactic stars with accurate MK types and parallaxes. TheHγ line and the continuum gradient are very good temperaturecriteria, the CHα_ {0} band and especially the Balmer jump forluminosity. The luminosity classification given for F to G supergiantcandidates in the LMC in the literature is often doubtful. 5 of the 23stars observed spectrophotometrically turn out to be probably galacticforeground dwarfs on the basis both of the Balmer jump and thecomparison of their flux distributions with synthetic ones based on theKurucz model atmospheres. Surface gravities derived purely on the basisof flux distributions and such ones given by models of stellar evolutionagree with each other for dwarfs and giants only. For supergiants theformer are about 1.0 dex higher than the latter. As a consequenceeffective temperatures and metallicities given by these two methodsdeviate from each other for such stars, too. The intrinsic colours andtemperatures of galactic and LMC supergiants do not differ. Withabsolute magnitudes up to -9.6 mag the upper luminosity limit in the LMCdoes not exceed that in the Galaxy, where Ia-0 supergiants haveMV of up to -9.5 mag. The metallicities of the supergiantsshow a rather large scatter. Nevertheless the mean metallicities of 0.02+/- 0.09 dex for the Galaxy and -0.26 +/- 0.10 dex for the LMC agreewell with other observations.
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HIPPARCOS photometry of 24 variable massive stars (alpha Cygni variables)
The photometric variability of 24 alpha Cyg variables, i.e. variablesuper-and hypergiants, observed by the Hipparcos satellite is described.Three of the selected stars are situated in the SMC, 12 in the LMC andthe remaining 9 in the Galactic plane. Four of them are hot S Dor-typevariables, or LBVs (luminous blue variables) and two are possiblemembers of this class. Light curves are presented for all stars. Forfive stars, among which one LBV, the variability was discovered from theHipparcos photometric data. Results of period searches are presentedand, when relevant, folded light curves are shown. The linear ephemerisof two variables was revised. For most of the program stars theHipparcos magnitude scale (Hp) differs from the V of the UBV system byla 0fm1 . For all variables temperatures and M_bol are given. Galacticforeground reddening for the objects in the Magellanic Clouds are givenbased on IRAS maps.
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A uvbyβ photometric calibration of iron abundances in supergiant stars.
A photometric reddening-free calibration for [Fe/H] valid for giant andsupergiant stars of intermediate temperature, has been obtained usingthe Stroemgren uvbyβ system. Galactic supergiants, supergiants inthe Magellanic Clouds and Galactic metal deficient red giants withspectroscopic determinations of [Fe/H] were used as calibrators. Thecalibration can be used to predict [Fe/H] with an accuracy of 0.33 dex,valid for stars with 0.14<[m_1_]<0.70 in the iron abundance range-2.5<[Fe/H]<+0.3. This shows the potential of supergiant stars astracers of iron abundances in other galaxies. Evidence that Galacticluminous F-G stars are intrinsically bluer than their counterparts inthe Magellanic Clouds is offered.
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On the motion of the Magellanic Clouds
We have measured the proper motion of the Large and Small MagellanicClouds using Magellanic Cloud stars in the PPM Catalogue, and obtainμ = 1.7+/-0.9 mas yr^-1^ for the LMC. Systematic uncertainties arediscussed. Bound and unbound orbits of the Magellanic Clouds around theGalaxy are consistent with our result. The various models of theMagellanic Stream and their predictions for the motion of the MagellanicClouds are discussed. The predictions by several authors for the sametype of model differ by up to 0.3 mas yr^-1^. All models proposed todate that assume the Magellanic Clouds to lead the Magellanic Streampredict a proper motion for the LMC of between 1.5 and 2.0 mas yr^-1^,the smallest value being a prediction for a Galaxy with no halo. Otherindependent measurements of the proper motion of the LMC are discussed.These lie between 1 and 1.5 mas yr^-1^. Future astrometry will have toallow measurement of the proper motion of the LMC with an uncertainty nolarger than one-tenth of a milliarcsecond per year in order to help todistinguish significantly between models of the halo of the Galaxy. Theproper motion of the LMC cannot by itself distinguish between models ofthe Magellanic Stream.
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Luminosities of yellow supergiants from near-infrared spectra - Calibration through Magellanic Cloud stars
The possibility of using medium resolution spectrograms in the nearinfrared region to determine luminosities of A-G supergiants has beenexplored. A sample of 49 of these stars has been observed in the twoMagellanic Clouds, and using the intensities of the O I 7774 triplet andan index (CP), which is a combination of the Ca II triplet and Paschenlines intensities, a preliminary luminosity calibration, based on LMCstars, has been obtained. Such a calibration predicts reliableluminosities for Galactic supergiants, and offers the advantage of beingcompletely reddening independent. The reddening free CP index combinedwith BVRI color indices has also been used to estimate the interstellarreddenings of Magellanic Cloud stars.
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Positional reference stars in the Magellanic Clouds
The equatorial coordinates are determined of 926 stars (mainly ofgalactic origin) in the direction of the Magellanic Clouds at the meanepoch T = 1978.4 with an overall accuracy characterized by the meanvalues of the O-C coordinates, Sa = 0.35 arcsec and Sd = 0.38 arcsec,calculated from the coordinates of the Perth reference stars. Thesevalues are larger than the accuracy expected for primary standard stars.They allow the new positions to be considered as those of reliablesecondary standard stars. The published positions correspond to anunquestionable improvement of the quality of the coordinates provided inthe current catalogs. This study represents an 'astrometric step' in thestarting of a 'Durchmusterung' of the Magellanic Clouds organized by deBoer (1988, 1989).
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The distance to the Magellanic Clouds from luminous F supergiants
A recent M(v)-uvby beta calibration for Galactic luminous F-Gsupergiants was used to estimate the distance to the Magellanic Cloudsfrom F supergiants. The distance moduli 19.33 + or - 0.31 for the SMCand 18.19 + or - 0.22 for the LMC are found. The present limitations ofusing F-G supergiants as distance indicators are discussed.
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CO overtone emission from Magellanic Cloud supergiants
A sample of 63 high-luminosity LMC supergiants has been searched forfirst-overtone CO emission at 2.3 microns. Six new CO emission starshave been found, showing that CO first-overtone emission is a commoncharacteristic of luminous stars with dense circumstellar envelopes andhaving a wide range of stellar temperatures. Of the non-CO emissionstars, eight have strong He I emission. Nine stars show CO absorption at2.3 microns from late-type companions. CO emission was not found in anyof the three LMC S Doradus variables, and the stars which do show COemission are not known to be photometrically variable.
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Photometric Studies of Magellanic Cloud Supergiants. II. Variability
Abstract image available at:http://adsabs.harvard.edu/abs/1986ApJS...62..451G
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Photometric studies of Magellanic Cloud supergiants. I - Mean magnitudes and reddenings. II - Variability
In the first part of this paper, a combination of spectral types for 81LMC and 46 SMC supergiants from the literature with new BVRI photometryyields reddenings and intrinsic colors for these stars. While reddeningsup to E(B-V) of 0.3 are found for the LMC sample, the figure for the SMCappears to be no more than 0.2. The dust/gas ratio in both galaxies isfound to be lower than in the Milky Way. In the second part, individualBVRI photoelectric observations for 88 LMC and 46 SMC intermediatespectral type supergiants are analyzed for variability. It is noted that45 percent of the stars exhibit significant variations, with theincidence of variability decreasing with decreasing luminosity.
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A photometric determination of the metal content for F-G type supergiants in the Large Magellanic Cloud
A VBLUW photometric analysis is used to derive the metal content of some100 F- and G type supergiants in the LMC. Using the empirical locus ofPel in the V-B/B-L diagram in conjunction with the relative dependenceof theoretical colors on the metal abundance, a metal deficiency of1.4-1.6 is found for the LMC stars in comparison with those in the solarneighborhood. With an average UBV system foreground reddening of E(B-V)= 0.05 for the LMC, these stars have a metal content of 0.66 + 0.11,-0.03 of the solar abundance. Agreement is found with the result ofprevious studies. Application to the derivation of the reddenings ofmost of the galactic supergiants is noted.
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Radial velocities of southern stars obtained with the photoelectric scanner CORAVEL. V - 404 F to M supergiant stars in the Large Magellanic Cloud
High accuracy radial velocities have been obtained for 404 F and Msupergiant stars belonging to the LMC using the photoelectric scannerCORAVEL. The observations are presented and the determination of theaccuracy is described. The results are compared to the previous work ofFeast et al. (1960), Ardeberg et al. (1972), and Brunet et al. (1973),and a new determination of the average velocity dispersion in the LMC isgiven. The general trend of the stellar velocities, as compared to theradial velocities of gaseous components, is examined. A systematic shiftof about 6 km/s between velocities of KM and OBA stars is observed,while agreement is excellent with H I velocities. The surfacedistribution of radial velocities shows a tendency of stars to clusterin groups with low intrinsic velocity dispersions. A preliminary meanvelocity dispersion of 5.3 km/s is determined for KM stars.
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Radial velocities from objective-prism plates in the direction of the Large Magellanic Cloud
A catalog is presented of 711 Large Magellanic Cloud (LMC) stars, withattention to the radial velocities of 418 of these. Also given are theradial velocities of 1127 galactic stars in the direction of the LMC, aswell as discussions of the precision of these measurements and of radialvelocity dispersion in different fields.
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VBLUW photometry of Magellanic Cloud super- and hypergiants, made in 1977 up to 1979
VBLUW photometry (Walraven system) is presented of SMC and LMC super-and hypergiants (super-supergiants). The observations were made between1977 and 1979. Also given are the values for V and B-V of the UBV system(with subscript J). The stability of the photometric parameters duringthe last 10-25 years is assessed by considering stars also treated byother investigators.
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DDO Observations of Southern Stars
Not Available
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A catalogue of A- and F-type supergiants in the Large Magellanic Cloud
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976A&AS...24...35S&db_key=AST
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UBV photometry for supergiants of the Large Magellanic Cloud
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975A&A....43..345B&db_key=AST
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Radial velocities from objective-prism plates in the direction of the Large Magellanic Cloud. List of 398 stars, LMC members. List of 1434 galactic stars, in the LMC direction
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974A&AS...13..173F&db_key=AST
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Rotation et masse DU grand nuage de Magellan.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973A&A....28..165P&db_key=AST
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Additional observations of supergiants and foreground stars in the direction of the Large Magellanic Cloud
Abstract image available at:http://adsabs.harvard.edu/abs/1973A&AS....9..447B
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Spectrographic and photometric observations of supergiants and foreground stars in the direction of the Large Magellanic Cloud
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&AS....6..249A&db_key=AST
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6-color photometry of 13 F-G supergiants in the Large Magellanic Cloud.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971A&A....15..320B&db_key=AST
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Five-colour photometry of supergiants and the dust-to-gas ratio in the Large Magellanic Cloud.
Abstract image available at:http://adsabs.harvard.edu/abs/1970A&A.....7...49V
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A deep objective-prism survey for Large Magellanic Cloud members
Not Available
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Grand Nuage de Magellan. Liste des etoiles membres DU Grand Nuage de Magellan et liste d'etoiles galactiques
Not Available
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INHABITED SKY
