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The present status of four luminous variables in M 33
Context: . Understanding the origin of the instabilities of LBVs isimportant for shedding light on the late evolutionary stages of massivestars and on the chemical evolution of galaxies. Aims: . Toinvestigate the physical nature of variable stars in the upper H-Rdiagram, we performed a spectrophotometric study of the Romano's star GR290 and the Hubble-Sandage variables A, B, and C in the close galaxy M33. Methods: . New spectroscopic and photometric data wereemployed in conjunction with already published data of these stars inorder to derive spectral types, energy distribution and bolometricluminosities. Results: . The yellow hypergiant Var A is still atminimum, with a ~G-type spectrum and strong Hα emission (W_eq≃ -35 Å). Var B is in a low luminosity hot state (V=17.5,B-V = -0.15) with very strong Hα emission (W_eq=-310 Å). Itsabsolute bolometric luminosity is 0.6× 106Lȯ. Var C, at V=16.4, is fainter than in the mid 1980s,but its spectrum shows the typical features of LBVs at maximum, aspectrum that is very rich in Fe ii emission lines. Its L_bol is about0.7× 106 Lȯ. The Romano's star GR 290has a rich hot emission-line spectrum and is very bright withL_bol=3× 106 Lȯ. During 2004 the starbrightened by ~half magnitude in each of the BVR filters. Conclusions: . Our observations confirm that Var A probably is anintermediate type hypergiant star surrounded by an expanding envelopewith a collisionally excited hydrogen emission, largely obscured bydusty disk and nebula. In recent years, Var B has undergone a bluewardtransition in the H-R diagram, probably at constant bolometricluminosity, while Var C is in a post-maximum phase with an ηCar-type spectrum. GR 290 is notable for its spectrum and luminosity,and it is likely to develop ample spectral variations in the nearfuture, similar to those observed in AG Car.
| Kinematic Masses of Super-Star Clusters in M82 from High-Resolution Near-Infrared Spectroscopy
Using high-resolution (R~22,000) near-infrared (1.51-1.75 μm) spectrafrom Keck Observatory, we measure the kinematic masses of two super-starclusters in M82. Cross-correlation of the spectra with template spectraof cool evolved stars gives stellar velocity dispersions ofσr=15.9+/-0.8 km s-1 for J0955505+694045(MGG-9) and σr=11.4+/-0.8 km s-1 forJ0955502+694045 (MGG-11). The cluster spectra are dominated by the lightof red supergiants and correlate most closely with template supergiantsof spectral types M0 and M4.5. King model fits to the observed profilesof the clusters in archival Hubble Space Telescope/Near-Infrared Cameraand Multi-Object Spectometer images give half-light radii ofrhp=2.6+/-0.4 pc for MGG-9 and rhp=1.2+/-0.17 pcfor MGG-11. Applying the virial theorem, we determine masses of1.5+/-0.3×106 Msolar for MGG-9 and3.5+/-0.7×105 Msolar for MGG-11 (where thequoted errors include σr, rhp, and thedistance). Population synthesis modeling suggests that MGG-9 isconsistent with a standard initial mass function (IMF), whereas MGG-11appears to be deficient in low-mass stars relative to a standard IMF.There is, however, evidence of mass segregation in the clusters, inwhich case the virial mass estimates would represent lower limits.Based on observations made at the W. M. Keck Observatory, which isoperated as a scientific partnership among the California Institute ofTechnology, the University of California, and the National Aeronauticsand Space Administration. The Observatory was made possible by thegenerous financial support of the W. M. Keck Foundation.
| V529 Coronae Austrinae: An RV Tauri Variable of Type RVb
We present an analysis of the photometric data on V529 CrA. The datainclude published photographic data as well as our ownUBV(RI)C measurements. Two dominant modulations with periodsof 23.571 and 761.5 days are present in the light curve. The double ofthe 23.571 day period (47.142 days) shows the alternating deep/shallowminima behavior of the RV Tauri class of variables, while the presenceof a longer modulation indicates a classification in the photometricsubclass RVb. Medium-resolution optical spectroscopy is also presented.Based partially on observations made at Laboratório Nacional deAstrofísica/CNPq, Brazil, and Cerro Tololo Inter-AmericanObservatory (CTIO), Chile.
| Quantitative spectral classification of galactic disc K-M stars from spectrophotometric measurements
New spectral observations for 47 southern galactic red supergiantsobtained with the new RUBIKON spectrophotometer (developed at theAstronomisches Institut der Ruhr-Universitat Bochum) at the Bochum 61-cmtelescope on La Silla are presented. The spectra range from 4800 to 7700A and their resolution is 10 A. The mean error of absolute fluxes is0.028 mag and that of relative fluxes 0.021 mag. The spectra will beavailable at the Strasbourg Stellar Database (CDS). Together with datataken from recently published spectral catalogues, the new observationshave been used to define spectral indices as measures of the strengthsof the following features: Fe i+TiOalpha_1, Mgb+TiOalpha_0,NaD+TiOgamma'_1, TiOgamma'_0 and TiOgamma_1 systems. The indices havebeen checked against errors introduced by reductions, interstellarreddening and different resolutions of different spectral catalogues,and have been found to be very insensitive to all these effects.Therefore, different catalogues may be combined without any loss ofaccuracy and homogeneity. The mean error of a single index has beenfound to be 0.011 mag. For stars from K4 to M7, a strong temperaturedependence is found for all indices. For the Fe i+TiO and especially theMgb+TiO features, a strong dependence on luminosity has also beenobserved. These indices therefore have been combined to form aluminosity index, while the others together form a spectral index. Thecombined indices have been calibrated in terms of MK data using thestepwise linear regression technique, and may be used for quantitativetwo- dimensional spectral classification of late K- and M-type stars.The mean error of the classification is 0.6 of spectral subtype and 0.8of luminosity class, which is much higher than would be expected fromthe uncertainty of the indices alone (which, e.g., for an M4 giantcorrespond to an uncertainty of 0.1 of spectral subtype and 0.3 ofluminosity class). This may be explained by the uncertainty of theoriginal MK classifications and the variability of some programme stars.
| 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 library of stellar spectra
Spectra for 161 stars having spectral classes O-M and luminosity classesV, III, and I have been incorporated into a library available onmagnetic tape. The spectra extend from 3510 to 7427 A at a resolution ofabout 4.5 A. The typical photometric uncertainty of each resolutionelement in the spectra is on the order of 1 percent while broad-bandvariations are smaller than 3 percent. Potential uses for the libraryinclude population synthesis of galaxies and clusters, tests of stellaratmosphere models, spectral classification, and the generation of colorindices having arbitrary wavelength and bandpass.
| Luminosity classification with the Washington system
The DDO 51 filter has been added to the Washington photometric system.The strong surface gravity sensitivity of the Mg I 'b' triplet and MgHbands which it monitors allows the system to easily discriminate betweendwarfs and giants of late G and K spectral type. The system isespecially suited as a membership criterion for abundance studies ofdistant cluster giants. The Mg index is insensitive to surface gravityvariations among G giants. The metallicity sensitivity among giants isalso relatively weak. Population I and II giants can be distinguishedbut no further differentiation is evident.
| UBV Photometry of Equatorial Stars
Not Available
| Nineteen new spectroscopic binaries and the rate of binary stars among F-M supergiants
Nineteen spectroscopic binaries (SBs) have been discovered in radialvelocity measurements made with the CORAVEL spectrophotometer on 181northern F-M supergiants. The rate of detected SBs among northern F-Msupergiants is 21 percent, without any dependence on spectral orluminosity class. The study of the binary F-M supergiants with knownorbital elements indicates that all the systems with a period smallerthan the critical value P(circ) have a nearly circular orbit. The valueof P(circ) depends on the luminosity class, being 400-600 d for class Iband 2000-7000 d for class Ia. This circularization of the orbits may bedue to the transfer of angular momentum during the phase of binary massexchange.
| The globular cluster system of the Galaxy. I - The metal abundances and reddenings of 70 globular clusters from integrated light measurements
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980ApJS...42...19Z&db_key=AST
| A photoelectric measurement of magnesium for late-type stars
A photoelectric index of MgH + Mg b for late-type stars has been createdby the addition of one filter bandpass to the DDO system. Measurementsshow that this index has good sensitivity to surface gravity for Kstars, and suggest that it can differentiate metal-poor halo giants fromdisk stars. From this index, involving measurement through two filtersalone, it appears that membership can be determined for stars on thegiant branch of globular clusters. It is possible that the index couldbe used, after calibration with cluster giants, to determine ages ofgiant stars in the field.
| The weak G band effect in M13, M92, NGC 6397 and M15.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977ApJ...215...74N&db_key=AST
| Mesures de vitesses radiales au spectrographe C de l'Observatoire de Haute Provence
Not Available
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Наблюдательные данные и астрометрия
| Созвездие: | Орёл |
| Прямое восхождение: | 19h43m05.45s |
| Склонение: | +09°29'21.8" |
| Видимая звёздная величина: | 7.829 |
| Собственное движение RA: | -0.3 |
| Собственное движение Dec: | -11.3 |
| B-T magnitude: | 9.309 |
| V-T magnitude: | 7.952 |
Каталоги и обозначения:
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