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Публикации по объекту
The Far Ultraviolet Spectroscopic Explorer Legacy in the Magellanic Clouds: An Online Stellar Sight Line Atlas
We present an atlas of stellar sight line data from the Far UltravioletSpectroscopic Explorer (FUSE) satellite for 287 stars in the MagellanicClouds, obtained from eight years of satellite operations. The intent ofour project is to make this rich ensemble data set accessible to a broadcommunity of researchers in a standardized format that will enable easyidentification of subsets of these data that are appropriate forpursuing specific science programs. We present the data in astandardized manner, showing key interstellar lines on a velocity scale,optical (MCELS) and infrared (Spitzer) sight line context images, andoverview plots of the spectral region containing the O VI??1032, 1038 doublet, and the entire 905-1187 Åspectral range observed with FUSE. Objects with multiple observationshave had their data summed to directly provide the highestsignal-to-noise ratio available. These data are accessible online as aHigh Level Science Product through the Multimission Archive at SpaceTelescope (MAST). In this article, we describe the data sets andprocessing, the atlas materials, and the MAST interface in detail, andalso provide examples of how to use these materials.
| Wra 751, a luminous blue variable developing an S Doradus cycle
Aims. The object Wra 751 is a luminous blue variable that latelyexhibits strong changes in light and color. We summarise the availablephotometry of Wra 751, present new photometric observations, and discussthese data with special attention on the systematic differences betweenthe various data sources. In addition, we establish an empiricalrelationship between b-y and B-V for this class of stars. Methods: Wra751 is a strong-active member of the S Dor class, and it exhibitsvery-long term S Doradus phases with an amplitude of about twomagnitudes in V and a cycle length of several decades. The associatedB-V colour-index amplitude is about 0.4 mag. At this moment this LBV,which is the reddest member of the class, is going through the bright(and red) stage of a long-term S Dor cycle. Results: The S Dorbehaviour of this system shows some resemblence to the temporalcharacteristics of the Galactic LBV AG Car, because the time scales andamplitudes of light and colour variability are very similar.Individual photometric measurements (Tables 2-4) are only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/484/463
| SN 2005 gj: evidence for LBV supernovae progenitors?
There is mounting observational evidence in favour of Luminous BlueVariables (LBVs) being the direct progenitors of supernovae. Here wepresent possibly the most convincing evidence yet for such progenitors.We find multiple absorption component P-Cygni profiles of hydrogen andhelium in the spectrum of SN 2005gj, which we interpret as being animprint of the progenitor's mass-loss history. Such profiles havepreviously only been detected in Luminous Blue Variables. This strikingresemblance of the profiles, along with wind velocities and periodsconsistent with those of LBVs leads us to connect SN 2005gj to an LBVprogenitor.Based on observations at the European Southern Observatory with UVES onthe VLT in programme 276.D-5020A and 078.D-0720.
| The Discovery of a P Cygni Analog in M31
We present spectroscopy and discuss the photometric history of apreviously obscure star in M31. The spectrum of the star is an extremelyclose match to that of P Cygni, one of the archetypes of luminous bluevariables (LBVs). The star has not shown much variability over the past40 years (<0.2 mag), although small-scale (0.05 mag) variations overa year appear to be real. Nevertheless, the presence of a subarcsecondextension around the star is indicative of a past outburst, and from thenebula's size (0.5 pc diameter) we estimate that the outburst took placeroughly 2000 years ago. P Cygni itself exhibits a similar photometricbehavior and has a similar nebula (0.2 pc diameter). We argue that thismay be more typical behavior for LBVs than commonly assumed. The star'slocation in the H-R diagram offers substantial support for stellarevolutionary models that include the effects of rotation, as the star isjust at a juncture in the evolutionary track of a 85 Msolarstar. The star is likely in a transition from an O star to a late-typeWN Wolf-Rayet star.Based in part on observations made with the NASA/ESA Hubble SpaceTelescope (HST), obtained from the Data Archive at the Space TelescopeScience Institute, which is operated by the Association for Universitiesfor Research in Astronomy (AURA), Inc., under NASA contract NAS 5-26555.
| The total-to-selective extinction ratio determined from near IR photometry of OB stars
The paper presents an extensive list of the total to selectiveextinction ratios R calculated from the infrared magnitudes of 597 O andB stars using the extrapolation method. The IR magnitudes of these starswere taken from the literature. The IR colour excesses are determinedwith the aid of "artificial standards" - Wegner (1994). The individualand mean values of total to selective extinction ratios R differ in mostcases from the average value R=3.10 +/-0.05 - Wegner (1993) in differentOB associations. The relation between total to selective extinctionratios R determined in this paper and those calculated using the "methodof variable extinction" and the Cardelli et al. (1989) formulae isdiscussed. The R values presented in this paper can be used to determineindividual absolute magnitudes of reddened OB stars with knowntrigonometric parallaxes.
| The Quadruple Wolf-Rayet System GP Cephei: Spectral Types, Masses, Mass-Loss Rate, and Colliding Winds
We have reevaluated the orbital elements for each pair of the quadruple(W-R+O) + (O+O) stellar system GP Cep and propose new spectral typesWN6o/WCE + O3-6, B0: I + B1: V-III. It is shown that there is only oneWolf-Rayet (W-R) star in GP Cep, contrary to a previous claim. A rate ofchange P=1.3+/-0.2 s yr-1 is determined for the W-R+O pair,which leads to a new period of 6.6887 days and to a W-R mass-loss rateof (0.8-3.0)×10-5 Msolar yr-1.Masses for this pair are estimated to be MW-R>~6Msolar and MO>~21 Msolar. Theeffects of wind-wind collision in the W-R+O pair are studied. It isshown that even after allowing for dilution by the OB components of thequadruple system, these effects are not as strong as in the binary V444Cygni (WN5+O6, P=4.212 days). In GP Cep, the phase-dependent, relativelyweak excess emission does not originate in the arms of the bow shockcone. Rather, it emerges from the extra heated portion of the W-R windfacing the hot O companion. The trailing bow shock arm is clearly seen,however, as an enhanced He I absorption component near quadrature atphase ~0.73. An anomalous blueshifted He I absorption is present atphase ~0.9, as is also seen in V444 Cyg, in the WC8+O9 I/O8 III binaryγ Velorum and in the LBV-cotype binary R81 (B2.5 Iab:e). A 3.5 dayorbit for the eclipsing B star pair is confirmed.
| The eclipsing hypergiant R 81 (B2.5Ia-O) in the Large Magellanic Cloud. System properties from spectroscopic and photometric monitoring
The eclipsing P Cygni-type star R 81 (HDE 269128, HIP 24080) of spectraltype B2.5 Ia-0 in the Large Magellanic Cloud was studied on the basis ofa long continuous time series with simultaneous high-resolution FEROSspectra and photometric measurements in the Strömgren system. Thestellar parameters derived for the primary are Teff = 19 500K and R = 96 Rsun. The orbital period of the binary is 74.566days. The mean light curve shows two eclipses, a brightness maximum justafter the eclipse of the hypergiant and a slow decline of brightnessbetween the two minima. For the first time, the orbital motion of theprimary has been detected. The system is close and eccentric (e=0.569)and both components nearly fill their Roche volumes. A spectralsignature of the companion of the hypergiant has not been found. Wesuspect that the secondary is embedded in a shell or disk of materialaccreted from the primary. In addition, line profile variations with aperiod of about 11 days, probably caused by non-radial pulsation, wereobserved. The line profiles indicate a strong wind from the primary withan outflow velocity of about 150 km s-1. Near primaryeclipse, strong absorptions in low excitation lines emerge abruptly thatpoint to an outflow of enhanced density and higher velocity in thedirection towards and beyond the secondary. Based on observationscollected with FEROS at the European Southern Observatory at La Silla,Chile, ESO proposal No. 62. H-0319. Tables 1 and 2 are only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/389/931
| S Doradus variables in the Galaxy and the Magellanic Clouds
The goal in writing this paper is five fold: (1) to summarize thescientific achievements in the 20th century on S Dor variables (orLBVs); (2) to present an inventory of these variables in the Galaxy andthe Magellanic Clouds with a description of their physical state andinstability properties; (3) to emphasize the photometric achievements ofthe various types of instabilities. Generally this seems to be aneglected item resulting in a number of misunderstandings continuouslywandering through literature; (4) to investigate the structure of the SDor-area on the HR-diagram; (5) to estimate the total numbers of S Dorvariables in the three stellar systems. The position of the strongactive S Dor variables in minimum brightness obey the following linearrelation on the HR-diagram:log L/Lsun = 1.37 log T_eff -0.03. The relatively small dispersion of less active and supposed ex-and dormant S Dor variables with respect to this relation is twice aslarge at the blue side than at the red side. This might be caused byevolution to the WR stage and/or to high rotation. S Dor variables canbe subject to five types of instabilities: the very rare genuineeruptive episodes (the ``SD-eruptions''), two different brighteningphases caused by slow pulsations (the ``SD-phases''): one on a timescale of years, the other on a time scale of decades at a more or lessconstant luminosity and two types of microvariations: one on a timescale of weeks, the other on a time scale of about 100 d. So far, noperiodicities of light curve characteristics of any of theseinstabilities have ever been found. The durations of active andnon-active stages are estimated for about half of the sample based onscattered magnitude estimations such as from historical records, and onmodern monitoring campaigns. It would be a misunderstanding to believethat all S Dor variables should be always spectacular. It is estimatedthat most of them will not be spectacular at all for at least 70% oftheir lifetime as an S Dor variable. Tables 1 to 6 and 8 to 17 are onlyavailable in electronic form at http://www.edpsciences.org, Table 7 isonly available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/366/508. Figures 2--10,12, 14, 15, 17--19 are only available in electronic form athttp://www.edpsciences.org, see Note added in proof
| Stars with the Largest Hipparcos Photometric Amplitudes
A list of the 2027 stars that have the largest photometric amplitudes inHipparcos Photometry shows that most variable stars are all Miras. Thepercentage of variable types change as a function of amplitude. Thiscompilation should also be of value to photometrists looking forrelatively unstudied, but large amplitude stars.
| UBV photometry of Galactic foreground and LMC member stars - III. LMC member stars - a new data base
New UBV photometry for 878 luminous member stars of the Large MagellanicCloud (LMC) and 13 stars of uncertain membership is presented. The datawill be available at Centre de Données astronomiques deStrasbourg. Including former observations now UBV data are available foraltogether 2470 luminous LMC stars and 2106 foreground stars plus 65stars of uncertain membership. The observations have been used alreadyfor several investigations dealing e.g. with interstellar reddeninglines and intrinsic colours, the dust distribution and the calibrationof charge-coupled device exposures.
| Simultanous spectroscopy and photometry of the eclipsing P Cygni star R81 of the LMC
R81 (B2.5Iab:e) of the LMC is the only known P Cygni type eclipsingbinary. During our guarantied time with the new Fiber fed Extended RangeOptical Spectrograph FEROS (spectral range 3700 Angstroms - 9200Angstroms; lambda/Deltalambda=48000) at the ESO 1.5m telescope weobtained a spectroscopic time series covering the whole period of 74.55d with a S/N ~ 100 and a time resolution of typically one spectrum pernight. Simultaneously we obtained the lightcurve of R81 at the Danish0.5 m telescope with a total phase coverage of typically one measurementper night. Due to the large spectral coverage of FEROS a huge amount ofstrategic lines could be indentified which allow to trace thephase-locked photospheric, wind and envelope behaviour of R81. Wepresent a first overview of the photometric and spectroscopic data.Several lines influenced differently by the wind are shown. Furthermorewe present preliminary orbital parameters from our first analyses of theradial velocity curve.
| 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.
| The HIPPARCOS proper motion of the Magellanic Clouds
The proper motion of the Large (LMC) and Small (SMC) Magellanic Cloudusing data acquired with the Hipparcos satellite is presented. Hipparcosmeasured 36 stars in the LMC and 11 stars in the SMC. A correctlyweighted mean of the data yields the presently available most accuratevalues, mu_alpha cos(delta) = 1.94 +/- 0.29 mas/yr, mu_delta = - 0.14+/- 0.36 mas/yr for the LMC. For the SMC, mu_alpha cos(delta) = 1.23 +/-0.84 mas/yr, mu_delta = - 1.21 +/- 0.75 mas/yr is obtained, whereby careis taken to exclude likely tidal motions induced by the LMC. Bothgalaxies are moving approximately parallel to each other on the sky,with the Magellanic Stream trailing behind. The Hipparcos proper motionsare in agreement with previous measurements using PPM catalogue data byKroupa et al. (1994), and by Jones et al. (1994) using backgroundgalaxies in a far-outlying field of the LMC. For the LMC the Hipparcosdata suggest a weak rotation signal in a clockwise direction on the sky.Comparison of the Hipparcos proper motion with the proper motion of thefield used by Jones et al. (1994), which is about 7.3 kpc distant fromthe center of the LMC, also suggests clockwise rotation. Combining thethree independent measurements of the proper motion of the LMC and thetwo independent measurements of the proper motion of the SMC improvesthe estimate of the proper motion of the LMC and SMC. The correspondinggalactocentric space motion vectors are computed. Within theuncertainties, the LMC and SMC are found to be on parallel trajectories.Recent theoretical work concerning the origin of the Magellanic Systemis briefly reviewed, but a unique model of the Magellanic Stream, forthe origin of the Magellanic Clouds, and for the mass distribution inthe Galaxy cannot yet be decided upon. Future astrometric space missionsare necessary to significantly improve our present knowledge of thespace motion of the two most conspicuous galactic neighbours of theMilky Way.
| On the spectrum of Theta Tucanae
We present 9700 visual-magnitude estimates of key objects among southernmassive stars, viz. the LBVs/hypergiants HD6884 (R40), eta Car, AG Car,HDE326823, HDE269006 (R71), HD33579, HDE269128 and WR stars HD5980 andWR40. The visual estimates are complemented with photoelectric lightcurves obtained over the last two decades in the framework of theLong-Term Photometry of Variables project. Several of our data sets havebeen searched for periodicities, and this aspect of the data iscommented in graphical form (by means of amplitude spectra) and, wherenecessary, with additional notes. The visual and photoelectric datademonstrate that the sytematic monitoring of luminous massive stars isscientifically very rewarding.
| Long-term visual monitoring of southern luminous variables
On the basis of high-resolution spectra and Stroemgren y photometry, wediscuss the nature of theta Tucanae as a (binary) delta Scuti star, andpresent a set of high-resolution digital spectra of theta Tuc togetherwith comparison spectra of the delta Scuti star UV Arietis. The spectrumof theta Tuc shows an amazing similarity to the spectrum of Procyon. Thepulsational radial velocity amplitude of theta Tuc (for the principaloscillation frequency) is of the order of 6-8 kms. The photometricindices point to Teff=7575 +/- 130 K, [Fe/H] = 0.02, L/Ldot =1.4 +/- 0.1and log g ~ 3.8. The estimated mass is not higher than 2.0 (+/- 0.1)Mdot, and the pulsation constant Q is about 30% smaller as waspreviously thought.
| 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.
| Longterm Photometry of Variables at ESO - Part Two - the Second Data Catalogue 1986-1990
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..102...79S&db_key=AST
| Observations of the atmospheres and winds of O-stars, LBV's and Wolf-Rayet stars
This review summarises recent studies of O-stars, Luminous BlueVariables (LBVs) and Wolf-Rayet (WR) stars, emphasising observations andanalyses of their atmospheres and stellar winds yielding determinationsof their physical and chemical properties. Studies of these stellargroups provide important tests of both stellar wind theory and stellarevolution models incorporating mass-loss effects. Quantitative analysesof O-star spectra reveal enhanced helium abundances in Of and manyluminous O-supergiants, together with CNO anomalies in OBN and Ofpe/WN9stars, indicative of evolved objects. Enhanced helium, and CNO-cycleproducts are observed in several LBVs, implying a highly evolved status,whilst for the WR stars there is strong evidence for the exposition ofCNO-cycle products in WN stars, and helium-burning products in WC and WOstars. The observed wind properties and mass-loss rates derived forO-stars show, in general terms, good agreement with predictions from thelatest radiation-driven wind models, although some discrepancies areapparent. Several LBVs show similar mass-loss rates at maximum andminimum states, contrary to previous expectations, with the mechanismresponsible for the variability and outbursts remaining unclear. WRstars exhibit the most extreme levels of mass-loss and stellar windmomenta. Whilst alternative mass-loss mechanisms have been proposed,recent calculations indicate that radiation pressure alone may besufficient, given the strong ionization stratification present in theirwinds.
| Redshifts of high-luminosity stars - The K effect, the Trumpler effect and mass-loss corrections
The Trumpler effect is demonstrated in B and A supergiants in h + ChiPersei, as well as in other associations of young luminous stars. TheK-Trumpler effect is also shown in O, B, and A supergiants in theMagellanic Clouds, as well as in nearby galaxies such as NGC 1569 and2777 and in blue irregular variables in M31 and M33. Mass outflow inluminous stars is shown to require an average correction of about 20km/s and to increase the excess redshifts of the stars in the MagellanicClouds to a significance level of 6 sigma. Completely empirical andindependent measurements show that mass-loss corrections of this sizeare required on average for supergiants in both the SMC and LMC and alsoin the Milky Way.
| Mapping AG Carinae - Long-slit spectroscopy and coronographic imaging of the nebula and jet
New high-resolution images of the nebula around the luminous bluevariable AG Carinae have been obtained with the Johns Hopkins AdaptiveOptics Coronograph at the Swope 40 inch (1 m) telescope, Las Campanas,in the light of H-alpha + forbidden N II and in a narrow V continuum.The images confirm the presence of highly axisymmetric features in AGCarinae's circumstellar environment. In addition, we present new, highsignal-to-noise ratio long-slit spectroscopic data, in the spectralrange (6363-7254 A), spatial resolution 0.89 arcsec/pixel, and spectralresolution 40 km/s, with full spatial coverage of the nebula. The radialvelocity data are consistent with a hollow, expanding shell but alsoshow noticeable deviations from spherical symmetry. Possibleinterpretations are examined, such as the presence of an equatorial diskdue to stellar rotation or, possibly, to a close, undetected companion,the presence of a magnetic field sufficiently strong to drive the wind,or density and pressure gradients in the local interstellar environment.
| Light variations of massive stars (Alpha Cygni variables). XIII - The B-type hypergiants R81 (LBV), HD 80077 (LBV?), HD 168607 = V 4029 Sagittarii (LBV) and HD 168625 = V 4030 Sagittarii
We present and discuss VBLUW and uvby photometry of four Alpha Cygvariables: the B-type hypergiants R81, HD 80077, HD 168607 = V 4029 Sgr,and HD 168625 = V 4030 Sgr. Quasi-periods of the light variations amountto 24,41 or 55,58 and 35 days, respectively. The maximum light amplitude(MLA) of R 81 and HD 168607 clearly reflects their LBV character. Thatfor HD 80077 suggests that it could be an LBV also. Normal Alpha Cygvariables and those which suffer from episodic mass loss eruptions, theLBVs appear to listen to the same P = constant lines in the HR diagram,but the light curves of both types show morphological differences.
| 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).
| IRAS 08005 - 2356 - A proto-planetary nebula with rapid mass loss
Photometric and spectroscopic observations of the cold infrared sourceIRAS 08005 - 2356 are presented. The infrared source is associated witha low-latitude F-type supergiant. Its optical spectrum shows strongH-alpha emission. In the red part of the spectrum numerous lowexcitation emission lines are present. H-alpha, H-beta and Na I D linesclearly show P Cyg profiles, indicative of mass loss from an extendedstellar atmosphere. Near-infrared photometry reveals the existence of ahot (1200 K) circumstellar dust shell. IRAS 08005 - 2356 is identifiedas a photo-planetary nebula. Its present-day mass loss rate is at least10 exp-6 solar mass/yr. At an estimated core mass of 0.6 solar mass thismeans that the object will turn into a planetary nebula within a 150years. Evidence is presented for a fast wind from the star, with outflowvelocities up to 400 km/s.
| Massive close binaries - Observations and evolutionary computations
An overview of research on massive close binary (MCB) evolution in thelate seventies and eighties is presented, and the processes involved inmassive close binaries are explained. The following aspects of the MCBevolution study are considered: definition and types; observations ofnon-evolved and evolved MCB; physical processes; and stellar wind massloss rates and convective core overshooting. A comparison between MCBobservations and evolutionary computations is made. For futuredevelopments of stellar evolution, physical studies and the determinatonof adequate abundances of carbon, oxygen and nitrogen of stars coveringthe whole massive star range are recommended.
| Long-term photometry of variables at ESO. I - The first data catalogue (1982-1986)
This paper presents the catalog of photometric data in the Stromgrensystem obtained during the first four years (October 1982 - September1986) of the Long-Term Photometry of Variables (LTPV) program at ESO.The data are available in computer-readable form.
| Discovery of a low mass B(e) supergiant in the Small Magellanic Cloud
A new peculiar B(e) supergiant has been discovered in the SmallMagellanic Cloud. High dispersion CASPEC observations and UBVRIJHKphotometry carried out at ESO were used to study the characteristics ofthis star. N82 shows strong P Cygni profiles of hydrogen Balmer linesand is very rich in emission lines of singly ionized iron, forbidden andpermitted. This star seems to be the lowest mass B(e) supergiant everdetected in the SMC. This is interesting for the question of the lowermass limit for the B(e) supergiants in the Magellanic Clouds. N82 may beconsidered as the missing link between the Magellanic B(e) supergiantsand the Galactic Be stars. N82 seems to have a late-type companion.
| Discovery of a low mass Be supergiant in the SMC.
Not Available
| The maximum amplitude of the optical micro-variations of massive O-F type stars (or Alpha Cygni variables, including LBV's or S DOR variables) across the HR diagram
The maximum light amplitude (MLA) of the microvariations of nearly 100massive stars with spectral type O 3-F8 are collected from theliterature and unpublished material. These variables, called the AlphaCygni variables, also include the LBVs or S Dor type variables. The SDor type variables must be in a quiescent stage to detect theirintrinsic variations properly. The log T(eff)/MLA diagram exhibits aclear separation between S Dor type variables and the normal Alpha Cygnivariables (the majority). The results suggest that the outer layers ofboth types of stars where gravity waves presumably occur, differphysically from each other.
| A Provisory Catalogue of S-Doradus Candidate Stars in the Magellanic Clouds
Not Available
| 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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Наблюдательные данные и астрометрия
| Созвездие: | Золотая Рыба |
| Прямое восхождение: | 05h10m22.78s |
| Склонение: | -68°46'23.8" |
| Видимая звёздная величина: | 10.507 |
| Собственное движение RA: | 1.4 |
| Собственное движение Dec: | -1.3 |
| B-T magnitude: | 10.485 |
| V-T magnitude: | 10.506 |
Каталоги и обозначения:
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