Contenuti
Immagini
Carica la tua immagine
DSS Images Other Images
Articoli relazionati
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.
| Wind properties of Wolf-Rayet stars at low metallicity: Sk 41 (SMC)
The stellar properties of Sk 41 (AB4, WN5h), the only known singleWolf-Rayet star in the SMC, are derived from ultraviolet (IUE), optical(AAT) and near-IR (NTT) spectroscopy. Contrary to expectations for lowmetal environments, the stellar properties of Sk 41 are typical ofequivalent WN stars in the Galaxy and LMC, with T* ~ 42kK,log(L/Lsun)=5.7, vinfty =1300 km s-1,H/He ~ 2 by number, and dot {M}/sqrt {f}=3x10-5Msunyr-1, where f is the volume filling factor.The stellar luminosity of Sk 41 is 50% below the minimum value predictedby single star evolutionary models at the metallicity of the SMC,suggesting a deficiency in present evolutionary models at lowmetallicity. Emission line luminosities of He II lambda 4686 and C IVlambda lambda 5801-12 in SMC WR stars are not systematically lower thantheir Galactic and LMC counterparts. From 43 late-type and 59 early-typeWN stars, log Llambda HeII= 36.0 ergs-1 and 35.8 erg s-1, respectively, while logLlambdaCIV =36.5 erg s-1. from 25early-type WC stars. This new calibration has application in deriving WRpopulations in young starburst galaxies. Synthetic WN models arecalculated with identical parameters except that metal abundances arevaried. Following the Smith et al. WN classification scheme, CNOequilibrium models reveal that earlier spectral types are predicted atlower metallicity, i.e. WN3-4 at 0.04Zsun versus WN6 at1.0Zsun. This provides an explanation for the trend towardsearlier WN spectral types at low metallicity. Based, in part, onobservations collected at the European Southern Observatory, La Silla,Chile (Proposal No. 61.D--0680 and 63.H--0683)
| VBLUW photometry of fifteen alpha CYG variables (including LBVs) in the Galaxy, the LMC and the SMC
VBLUW photometry (Walraven system) of 15 alpha Cyg-type variables,(luminous massive stars), including 10 LBVs and one suspected LBV arepresented. Formulae are given to transform the V and V-B of the Walravensystem to V and B-V of the Johnson UBV system.
| Light variations of massive stars (alpha Cyg variables). XVI. The LMC supergiants R 85 (LBV) and R 110 (LBV) and the SMC supergiants R 42 and R 45
Multi-colour photometry of four variable supergiants in the LMC and SMC,viz. R 85, R 110, R 42 and R 45, is searched for periods, studied anddiscussed. The suspected LBV R 85 is undoubtedly an active LBV, thoughnot as spectacular as R 110. Their microvariations superimposed on the SDor-activity are analyzed as well as those exhibited by R 42 and R 45.Often, a period search is difficult because of the very complicatedmicro-variability. We suggest that this is caused by an intricatemulti-cyclic behaviour combined with stochastic processes. The length ofthe strongest cyclicity in the power spectrum of R 42 (128 d) is of theorder of the rotation periods of BA-type supergiants. In connection withour findings described in the present paper and the previous ones, wediscuss various competing theoretical models on the instability of alphaCyg variables, including the LBVs. Based on observations obtained at theEuropean Southern Observatory at La Silla, Chile (observing proposals55D-0317, 56D-0249, 57D-0133 and 58D-0118)
| Cyclicities in the light variations of Luminous Blue Variables. II. R40 developing an S Doradus phase
Stroemgren differential photometry of R40 collected during the timeinterval 1986-1996 is analysed together with Walraven photometry. Thegradual brightening of the star over the last 10 years can be describedby a linear trend with superimposed oscillations (in v, b and y) withfrequency 0.0008cd(-1) ( ~ 1300 d cycle). We interpret theseoscillations as ``normal S Dor'' phases, and suggest that thequasi-linear brightening of the star is the ascending branch of agrowing very-long-term S Dor phase (VLT-SD), as found by van Genderen etal. (1997a) in AG Car and S Dor itself. As R40 is now becoming fainterand bluer, the length of the VLT-SD cycle is about 20 years. Based onobservations obtained at the European Southern Observatory at La Silla,Chile (applications ESO 56D-0249 and 58D-0118)
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| A catalog of far-ultraviolet point sources detected with the fast FAUST Telescope on ATLAS-1
We list the photometric measurements of point sources made by the FarUltraviolet Space Telescope (FAUST) when it flew on the ATLAS-1 spaceshuttle mission. The list contains 4698 Galactic and extragalacticobjects detected in 22 wide-field images of the sky. At the locationssurveyed, this catalog reaches a limiting magnitude approximately afactor of 10 fainter than the previous UV all-sky survey, TDl. Thecatalog limit is approximately 1 x 10-14 ergs A sq cm/s,although it is not complete to this level. We list for each object theposition, FUV flux, the error in flux, and where possible anidentification from catalogs of nearby stars and galaxies. Thesecatalogs include the Michigan HD (MHD) and HD, SAO, the HIPPARCOS InputCatalog, the Position and Proper Motion Catalog, the TD1 Catalog, theMcCook and Sion Catalog of white dwarfs, and the RC3 Catalog ofGalaxies. We identify 2239 FAUST sources with objects in the stellarcatalogs and 172 with galaxies in the RC3 catalog. We estimate thenumber of sources with incorrect identifications to be less than 2%.
| Runaway stars from young star clusters containing initial binaries. II - A mass spectrum and a binary energy spectrum
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990AJ.....99..608L&db_key=AST
| A catalog of ultraviolet interstellar extinction excesses for 1415 stars
Ultraviolet interstellar extinction excesses are presented for 1415stars with spectral types B7 and earlier. The excesses with respect to Vare derived from Astronomical Netherlands Satellite (ANS) 5-channel UVphotometry at central wavelengths of approximately 1550, 1800, 2500, and3300 A. A measure of the excess extinction in the 2200-A extinction bumpis also given. The data are valuable for investigating the systematicsof peculiar interstellar extinction and for studying the character of UVinterstellar extinction in the general direction of stars for which theextinction-curve shape is unknown.
| The galactic reddening law - The evidence from uvby-beta photometry of B stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985A&A...142..189T&db_key=AST
| On the nature of early-type stars in the galactic halo
Effective temperatures and surface gravities of 46 intermediate and highgalactic latitude OB stars have been estimated from Stromgren /C1/ andH-beta photometry. In addition, helium, calcium and magnesium abundancesrelative to hydrogen have been derived for eleven stars. The typicalOB-type stellar parameters indicate that they are normal Population Istars, several of which require ejection velocities of more than 100km/s from the plane in order to reach their present z-distances duringtheir lifetimes. The observed correlation between peculiar velocity andmass for stars with /z/ not less than 400 pc is compatible with theBlaauw runaway hypothesis as the acceleration mechanism. A plot of logN(Na I) versus E(B-V) implies that the gas-to-dust ratio in the halo isprobably similar to that found for material in the galactic disc. Thisimplies that the sputtering of calcium from grain surfaces is probablyresponsible for the observed velocity dependence of the N(Na I)/N(Ca II)ratio.
| A study of interstellar absorption at high galactic latitudes. I - Highly ionized gas
IUE interstellar absorption line data for C IV, Si IV, N V and Fe II, ina sample of 24 distant, early-type stars at high galactic latitudes, areanalyzed with other published results in order to study the distributionand physical conditions of highly ionized gas in the halo of the Galaxy.The C IV and Si IV lines, which are detected in front of approximatelytwo-thirds of the stars observed, are significantly stronger that thoseobserved in the spectra of disk stars of similar spectral types, andtheir velocities show no correlation with the velocities of thebackground stars. The observed variation of the column densities of C(3+) and Si (3+) with distance z from the plane is consistent with thesuggested existence of a Galactic transition layer between cool gas inthe disk and outer halo regions at temperatures greater than thoseobservable with IUE. Attention is drawn to the fact that the observed C(3+)/Si (3+) ratio may be a characteristic signature of hot gas ingalactic halos.
| H-beta photometry of southern early-type stars
H-beta photoelectric photometry is presented for 209 southern hemisphereearly-type stars from the HD catalog with galactic latitudes /b/ greaterthan 6 deg. Four-color photometry exists for all these stars and MKtypes for most of them. Absolute magnitudes have been estimated for allbut the emission-line stars and distances from the sun and the galacticplane determined.
| Ultraviolet absorption by interstellar gas at large distances from the galactic plane
Eighteen high-dispersion IUE spectra of six stars in the LargeMagellanic Cloud, three stars in the Small Magellanic Cloud, and twoforeground stars were analyzed. Fourteen spectra cover the wavelengths1150-2000 A, and four cover 1900-3200 A; the velocity resolution isabout 25 km/s. All the Magellanic Cloud spectra exhibit very stronginterstellar absorption lines due to a wide range of ionization stagesat galactic velocities and at velocities associated with the IMC or SMC.The observational results are related to current theoretical ideas aboutthe origin and physical state of gaseous galactic halos; the analysis isrestricted to the Milky Way absorption features.
| Five-colour photometry of blue stars in the Magellanic-Cloud region
The results of photoelectric observations of about 500 stars in andbetween the Magellanic Clouds are given. The observations were made inthe Walraven VBLUW-system. Within the limits of the study, no cloudmembers are found to be associated with the neutral hydrogen between theclouds. Seventy-five stars, previously reported to be cloud members byothers, were found independently. A large number of new members of thewing system of the SMC are identified. The great eastward extension ofthe wing system is clearly illustrated by the results
| Four colour photometry of southern early-type stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978MNRAS.182..629K&db_key=AST
| Properties of the Walraven VBLUW photometric system
The Walraven five-channel (VBLUW) photometer has been used primarily tostudy Cepheids and RR Lyrae variables. Those properties of the VBLUWphotometric system are discussed which are important for analyzing andinterpreting data on such stars. The standard stars that define thesystem are examined, the long-term stability of these stars is examined,and the responses of the photometric passbands are analyzed. Correctionsfor atmospheric extinction and interstellar reddening are reviewed,noting that color terms in the extinction corrections are sufficientlysmall to be neglected and that nonlinear terms in reddening correctionscan also be neglected provided the reddening is not higher than about1.25 magnitudes. Application of the VBLUW system to the classificationof A, F, and G stars, Hyades main-sequence stars, bright field stars,and subdwarfs is demonstrated, and observed two-color diagrams arecompared with theoretical diagrams based on model atmospheres. It isconcluded that a three-dimensional classification based on effectivetemperature, surface gravity, and heavy-element abundance is possiblefor A, F, and G spectral types and that VBLUW photometry is more thantwice as sensitive as Stroemgren uvby photometry to differences inheavy-element abundances below 8000 K.
| Interstellar lines in stars at high galactic latitudes.
Abstract image available at:http://adsabs.harvard.edu/abs/1974ApJ...194...37C
| Polarization measurements of stars in the Magellanic Clouds.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970AJ.....75..778M&db_key=AST
| Photometry and spectral classification of early-type stars away from the galactic plane.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970MNRAS.150...23H&db_key=AST
|
Sottometti un nuovo articolo
Link relazionati
Sottometti un nuovo link
Membro dei seguenti gruppi:
|
Osservazione e dati astrometrici
| Costellazione: | Idro |
| Ascensione retta: | 01h41m17.90s |
| Declinazione: | -75°39'49.1" |
| Magnitudine apparente: | 8.139 |
| Distanza: | 495.05 parsec |
| Moto proprio RA: | 11.2 |
| Moto proprio Dec: | 13.8 |
| B-T magnitude: | 7.983 |
| V-T magnitude: | 8.127 |
Cataloghi e designazioni:
|
