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Quantitative Stellar Spectral Classification. IV. Application to the Open Cluster IC 2391
In this work we perform the first test of a stellar spectralclassification method (Stock & Stock 1999) by applying it to earlytype stars. The sample of stars are the members of the open cluster IC2391 that have high-resolution spectra available in the UVES Project ofParanal Observatory. We show that, in general, absolute magnitudes M_Vand intrinsic colors (B-V)_0 can be recovered within the uncertaintiesstated in the original calibration (˜ 0.4 for the magnitudes and˜ 0.03 for the colors). This accuracy allows us to estimatedistances and to infer membership of individual stars to obtain anaverage distance to the cluster of 156+/-24 pc, which is in goodagreement with previously reported determinations. Finally, we identifyand discuss the real strengths and limitations of this method and wesuggest how it can be improved for future studies.
| Chemical Composition in Fast Rotators Main Sequence Stars
Using public data of the Ultraviolet and Visual Echelle SpectrographParanal Observatory Project (UVES) the projected rotational velocities,v sin i, for 16 stars in the field of the galactic cluster IC 2391 (oVel Cluster) were obtained using the method of the Fourier transform(FT). We found that only 12 of these objects are cluster members andseparating them in two sets (main sequence stars and evolved stars) acorrelation of the rotation velocity with the effective temperature wasfound, indicating a nearly equal orientation of the rotation axis forthe member stars. The ratios N/C and O/C obtained for the main sequencestars increase with v sin i and show evidence of mixing induced byrotation.
| Kinematics of the Scorpius-Centaurus OB association
A fine structure related to the kinematic peculiarities of threecomponents of the Scorpius-Centaurus association (LCC, UCL, and US) hasbeen revealed in the UV-velocity distribution of Gould Belt stars. Wehave been able to identify the most likely members of these groups byapplying the method of analyzing the two-dimensional probability densityfunction of stellar UV velocities that we developed. A kinematicanalysis of the identified structural components has shown that, ingeneral, the center-of-mass motion of the LCC, UCL, and US groupsfollows the motion characteristic of the Gould Belt, notably itsexpansion. The entire Scorpius-Centaurus complex is shown to possess aproper expansion with an angular velocity parameter of 46 ± 8 kms‑1 kpc‑1 for the kinematic centerwith l 0 = ‑40° and R 0 = 110 pc found.Based on this velocity, we have estimated the characteristic expansiontime of the complex to be 21 ± 4 Myr. The proper rotationvelocity of the Scorpius-Centaurus complex is lower in magnitude, isdetermined less reliably, and depends markedly on the data quality.
| Spitzer 24 μm Observations of Open Cluster IC 2391 and Debris Disk Evolution of FGK Stars
We present 24 μm Spitzer MIPS photometric observations of the ~50 Myropen cluster IC 2391. Thirty-four cluster members ranging in spectraltype from B3 to M5 were observed in the central square degree of thecluster. Excesses indicative of debris disks were discovered around oneA star, six FGK stars, and possibly one M dwarf. For the cluster membersobserved to their photospheric limit, we find a debris disk frequency of10+17-3% for B-A stars and31+13-9% for FGK stars using a 15% relative excessthreshold. Relative to a model of decaying excess frequency, thefrequency of debris disks around A-type stars appears marginally low forthe cluster's age while that of FGK stars appears consistent. Scenariosthat may qualitatively explain this result are examined. We concludethat planetesimal activity in the terrestrial region of FGK stars iscommon in the first ~50 Myr and decays on timescales of ~100 Myr.Despite luminosity differences, debris disk evolution does not appear todepend strongly on stellar mass.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| X-ray spectral and timing characteristics of the stars in the young open cluster IC 2391
We present X-ray spectral and timing analysis of members of the youngopen cluster IC 2391 observed with the XMM-Newton observatory. Wedetected 99 X-ray sources by analysing the summed data obtained fromMOS1, MOS2 and pn detectors of the EPIC camera; 24 of them are members,or probable members, of the cluster. Stars of all spectral types havebeen detected, from the early-types to the late-M dwarfs. Despite thecapability of the instrument to recognize up to 3 thermal components,the X-ray spectra of the G, K and M members of the cluster are welldescribed with two thermal components (at kT1 0.3-0.5keV and kT2 1.0-1.2 keV respectively) while the X-rayspectra of F members require only a softer 1-T model. TheKolmogorov-Smirnov test applied to the X-ray photon time series showsthat approximately 46% of the members of IC 2391 are variable with aconfidence level >99%. The comparison of our data with those obtainedwith ROSAT/PSPC, nine years earlier, and ROSAT/HRI, seven years earlier,shows that there is no evidence of significant variability on thesetime scales, suggesting that long-term variations due to activity cyclessimilar to that on the Sun are not common, if present at all, amongthese young stars.
| Data mining in the young open cluster IC2391
Large-scale astrometric and photometric data bases have been used tosearch for and confirm stellar membership of the open cluster IC2391.125 stars were found that satisfied criteria for membership based onproper motion components and BRI photometry from the United States NavalObservatory B (USNO-B) catalogue and JHK photometry from the Two MicronAll Sky Survey (2MASS) catalogue. This listing was compared with othersrecently published. A distance to the cluster of 147.7 +/- 5.5 pc wasfound with mean proper motion components, from the Tycho2 catalogue of(-25.04 +/- 1.53 masyr-1+23.19+/-1.23 masyr-1). Arevised Trumpler classification of II3r is suggested. Luminosity andmass functions for the candidate stars were constructed and comparedwith those of field stars and other clusters.
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| Seven-Color Photoelectric Photometry of the Omicron Velorum Cluster
Photoelectric observations in the Vilnius seven-color photometric systemof 36 stars in the magnitude range 3.6 < V < 10.7 in the opencluster around the star o Velorum are presented. Photometric spectraland luminosity classes are determined for each star from which the meandistance modulus of the cluster is found to be 5.94+/-0.02 mag and themean color excess EY-V = 0.00+/-0.02 mag. The membership ofthe cluster stars is discussed.
| Open clusters with Hipparcos. I. Mean astrometric parameters
New memberships, mean parallaxes and proper motions of all 9 openclusters closer than 300 pc (except the Hyades) and 9rich clusters between 300 and 500 pc have been computed using Hipparcosdata. Precisions, ranging from 0.2 to 0.5 mas for parallaxes and 0.1 to0.5 mas/yr for proper motions, are of great interest for calibratingphotometric parallaxes as well as for kinematical studies. Carefulinvestigations of possible biases have been performed and no evidence ofsignificant systematic errors on the mean cluster parallaxes has beenfound. The distances and proper motions of 32 more distant clusters,which may be used statistically, are also indicated. Based onobservations made with the ESA Hipparcos astrometry satellite
| 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.
| The Evolution of Stellar Coronae: Initial Results from a ROSAT PSPC Observation of IC 2391
Not Available
| The IC 2391 supercluster
Sixty-three field stars and the sparse cluster IC 2391 have beenidentified as members of the IC 2391 supercluster. The members have atleast 95 percent of their space motion, directed toward (A,D) = (5.82h,- 12.44d). Like members of the very similar Pleiades supercluster, theIC 2391 supercluster contains objects of two ages: t = 8 x 19 exp 7 and2.5 x 10 exp 8 yr. A prototype very active chromosphere star and theenigmatic giant variable TZ For are supercluster members together withtwo A-type stars suspected of possessing particulate disks. Anespecially interesting member is the system of Xi Cep (HR 8417) in whichthe two brightest components are greatly undermassive.
| Radial velocities in the open cluster IC 2391
Radial velocities have been determined for 31 stars in the field of theopen cluster IC 2391, and the percentage of probable radial-velocityvariables is derived. The orbit of one previously known spectroscopicbinary is improved, and the existence of two double-line binaries isconfirmed. The membership to the cluster and the average cluster radialvelocity are discussed and the incidence of short-period binaries amongthe Main-Sequence members of IC 2391 is compared with the incidence forother clusters with similar average axial rotation of its members.
| The early A type stars - Refined MK classification, confrontation with Stroemgren photometry, and the effects of rotation
The MK classification system for the early A-type stars is refined, anda parallel system of standards for the broad-lined stars is introduced.With this improved system, stars may be classified with significantlygreater precision than before. It is shown that spectral types in thissystem are not systematically affected by rotational line broadening. Atotal of 372 early A-type stars are classified, and a confrontation ofthese spectral types with Stroemgren photometry reveals a number ofsystematic photometric effects of rotation. In particular, high v sin istars are systematically redder than low v sin i stars of the samespectral type, and the beta index is weakened by rotation. It isconcluded that precise spectral classification in conjunction withStroemgren and H-beta photometry can potentially provide a valuablecheck and input to the theory of the atmospheres of rotating stars.
| Photoelectric search for CP2-stars in open clusters. VIII - IC 2391 and NGC 2451
Delta-a photometry for 90 stars in the areas of the rather young openclusters IC 2391 and NGC 2451, covering the whole spectral domain ofCP2-stars, is presented. Seven stars show up as photometricallypeculiar, but membership is probable only for 4, 2 for each cluster. NGC2451 may have to be divided into a near and a far cluster. IC 2391 isunreddened and presents itself as ideal reference for the normality linein the Delta-a photometry. Crawford's (1978) calibration yields absolutemagnitudes for the peculiar stars which result in distance moduli veryclose to the mean cluster modulus. Again it is possible to confront thediversity of spectral classifications with the photometric peculiarityindex Delta-a.
| Observed and computed spectral flux distribution of non-supergiant O9-G8 stars. III - Determination of T(eff) for the stars in the Breger Catalogue
The effective temperatures and angular diameters of nonsupergiant O9-G8stars are determined from visible spectrophotometry. The results, whichrefer to 302 stars included in the Breger Catalogue, are derived fromthe comparison between the observed flux distributions and thepredictions of Kurucz's models (1979). The uncertainties to be expectedin individual results are discussed; their sizes are of the order of 5percent in effective temperature and 10 percent in angular diameter.
| The common origin of some open clusters
Eight open clusters have been observed with uvby-beta photometry and forseven of them the metal abundances have been determined. Six of thesehave similar metallicities. They are close in space and are also knownto have similar ages and radial velocities. These clusters are suspectedof having a common origin. Some studies are made of the reliability ofthe photometric system. A large gain in limiting magnitude can beachieved against an unimportant loss of accuracy if interference filtersare removed.
| Axial rotational velocities in the open cluster IC 2391
Projected rotational velocities have been determined for the members ofthe open cluster IC 2391. The results are discussed in the context ofthe statistical relation between axial rotation and percentage ofbinaries found by Abt (1962) for open clusters and associations.
| Spectral morphology in the open cluster IC 2391
Thirty-one stars brighter than B = 10 in the field of the open clusterIC 2391 are classified on the basis of the mean and MK dispersion. Byusing only normal stars of the main sequence and the absolute visualmagnitudes taken from the calibration made by Garrison (1978), adistance modulus of 5.9 + or - 0.07 (p.e.) magnitudes has been obtainedwhich corresponds to a distance of about 150 pc. A new Am star has beendiscovered, and the presence of two more, discovered earlier, has beenconfirmed. The spectra of the Silicon star HD 74535 and of a Si-Cr-Srobject are characterized.
| Positions of stars in regions of 14 southern galactic clusters
Positions have been obtained for a total of 3487 stars scattered over 14regions that are centered on each of the southern galactic clusters NGC1981, 2287, 2437, 2451, 2516, 2546, 2547, 2548, 3114, 3532, IC 2391,2395, 2602, and Truempler 10. A frame of reference has been establishedfor each region using ESO Schmidt plates centered on the clusters, witheach plate containing 20-35 measurable Perth 70 stars that are used fordetermining the positions of 200-400 fainter stars within a centralfield of 25 min of arc radius (covering the corresponding 1.5-m plates).
| Six clusters in Puppis-Vela
Intermediate band and H-beta observations of stars in the clusters NGC2451, Cr 140, Cr 135, Cr 173, IC 2391, and Cr 132 in Puppis-Vela arediscussed. Photometric and astrometric parameters for the stars areshown and discussed, along with light and color curves, color-luminosityarrays, histograms for reddening and luminosity, and stellardistributions. Cr 132 consists mainly of members of CMa OB2 plus a fewstars that may be an extension of Cr 140. The latter is an elongatedcluster of some 20 stars, 450 pc distant, 30 million years old, and with(U,V,W) = (+27,-6,-16) km/s. Cr 135 has only eight members, including aK2 Ib star, some 30 million years old, 310 pc distant, and (U,V,W) =(+13,-11,-12) km/s. For NGC 2451, extensive photometry reveals nocluster. Cr 173 is in the Vela sheet and may contain Gamma Vel and thecepheid AH Vel. IC 2391 is a very extended cluster including about twodozen stars brighter than the sun, some 30 million years old and 165 pcdistant, with (U,V,W) = (+20,-19,-3) km/s.
| Search for chromospheres in A-type stars
A search for chromospheric emission in the Ca II H and K lines was madefor eight main-sequence A-stars in the young clusters C 0838-528 (IC2391) and in the Hyades, where (at least later-type) stars havegenerally enhanced chromospheric activity, making possible emissioneasier to detect. No evidence for emission was found in these stars andnor in Sirius (A 1 V).
| Relative radial velocities from objective prism spectra in the region of nine southern open star clusters and a star field at Eta Carinae
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&AS...41..245G&db_key=AST
| A comparison of observations with main-sequence evolutionary models.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977PASP...89..554P&db_key=AST
| Catalog of spectrophotometric scans of stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976ApJS...32....7B&db_key=AST
| Rotational Velocities in IC 2391
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974PASP...86..940L&db_key=AST
| The Evolutionary Status of the Blue Halo Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973ApJS...26...37N&db_key=AST
| NGC 2516 and the Pleiades Group
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972ApJ...173...63E&db_key=AST
| K-Line Photometry of Stars in Population i Clusters
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971ApJS...23..453H&db_key=AST
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