Оглавление
Изображения
Загрузить ваше изображение
DSS Images Other Images
Публикации по объекту
CHARM2: An updated Catalog of High Angular Resolution Measurements
We present an update of the Catalog of High Angular ResolutionMeasurements (CHARM, Richichi & Percheron \cite{CHARM}, A&A,386, 492), which includes results available until July 2004. CHARM2 is acompilation of direct measurements by high angular resolution methods,as well as indirect estimates of stellar diameters. Its main goal is toprovide a reference list of sources which can be used for calibrationand verification observations with long-baseline optical and near-IRinterferometers. Single and binary stars are included, as are complexobjects from circumstellar shells to extragalactic sources. The presentupdate provides an increase of almost a factor of two over the previousedition. Additionally, it includes several corrections and improvements,as well as a cross-check with the valuable public release observationsof the ESO Very Large Telescope Interferometer (VLTI). A total of 8231entries for 3238 unique sources are now present in CHARM2. Thisrepresents an increase of a factor of 3.4 and 2.0, respectively, overthe contents of the previous version of CHARM.The catalog is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/431/773
| Lithium and rotation in F and G dwarfs and subgiants
Lithium abundances have been determined in 127 F and G Pop I stars basedon new measurements of the equivalent width of the lambda 6707 ÅLi I line from their high resolution CCD spectra. Distances and absolutemagnitudes of these stars have been obtained from the HipparcosCatalogue and their masses and ages derived, enabling us to investigatethe behaviour of lithium as a function of these parameters. Based ontheir location on the HR diagram superposed on theoretical evolutionarytracks, the sample of the stars has been chosen to ensure that they havemore or less completed their Li depletion on the main sequence. A largespread in the Li abundances is found at any given effective temperatureespecially in the already spun down late F and early G stars. Thisspread persists even if the ``Li-dip'' stars that have evolved from themain sequence temperature interval 6500-6800 K are excluded. Stars inthe mass range up to 2 M/Msun when divided into threemetallicity groups show a linear correlation between Li abundance andmass, albeit with a large dispersion around it which is not fullyaccounted for by age either. The large depletions and the observedspread in Li are in contrast to the predictions of the standard stellarmodel calculations and suggest that they are aided by non-standardprocesses depending upon variables besides mass, age and metallicity.The present study was undertaken to examine, in particular, the effectsof rotation on the depletion of Li. No one-to-one correlation is foundbetween the Li abundance and the present projected rotational velocity.Instead the observed abundances seem to be dictated by the rotationalhistory of the star. However, it is noted that even this interpretationis subject to the inherent limitation in the measurement of the observedLi EQW for large rotational velocities.Table 1 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/409/251
| The Wilson-Bappu effect: A tool to determine stellar distances
Wilson & Bappu (\cite{orig}) have shown the existence of aremarkable correlation between the width of the emission in the core ofthe K line of Ca II and the absolute visual magnitude of late-typestars.Here we present a new calibration of the Wilson-Bappu effect based on asample of 119 nearby stars. We use, for the first time, widthmeasurements based on high resolution and high signal to noise ratio CCDspectra and absolute visual magnitudes from the Hipparcos database.Our primary goal is to investigate the possibility of using theWilson-Bappu effect to determine accurate distances to single stars andgroups.The result of our calibration fitting of the Wilson-Bappu relationshipis MV=33.2-18.0 log W0, and the determinationseems free of systematic effects. The root mean square error of thefitting is 0.6 mag. This error is mostly accounted for by measurementerrors and intrinsic variability of W0, but in addition apossible dependence on the metallicity is found, which becomes clearlynoticeable for metallicities below [Fe/H] ~ -0.4. This detection ispossible because in our sample [Fe/H] ranges from -1.5 to 0.4.The Wilson-Bappu effect can be used confidently for all metallicitiesnot lower than ~ -0.4, including the LMC. While it does not provideaccurate distances to single stars, it is a useful tool to determineaccurate distances to clusters and aggregates, where a sufficient numberof stars can be observed.We apply the Wilson-Bappu effect to published data of the open cluster M67; the retrieved distance modulus is of 9.65 mag, in very goodagreement with the best distance estimations for this cluster, based onmain sequence fitting.Observations collected at ESO, La Silla.
| 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
| Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Spectroscopic binary orbits from photoelectric radial velocities. Paper 148: HR 7955
Not Available
| A catalog of rotational and radial velocities for evolved stars
Rotational and radial velocities have been measured for about 2000evolved stars of luminosity classes IV, III, II and Ib covering thespectral region F, G and K. The survey was carried out with the CORAVELspectrometer. The precision for the radial velocities is better than0.30 km s-1, whereas for the rotational velocity measurementsthe uncertainties are typically 1.0 km s-1 for subgiants andgiants and 2.0 km s-1 for class II giants and Ib supergiants.These data will add constraints to studies of the rotational behaviourof evolved stars as well as solid informations concerning the presenceof external rotational brakes, tidal interactions in evolved binarysystems and on the link between rotation, chemical abundance and stellaractivity. In this paper we present the rotational velocity v sin i andthe mean radial velocity for the stars of luminosity classes IV, III andII. Based on observations collected at the Haute--Provence Observatory,Saint--Michel, France and at the European Southern Observatory, LaSilla, Chile. Table \ref{tab5} also available in electronic form at CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Lithium abundance and mass
Observations of cool giants have shown that there exists a large rangein their lithium abundances even for apparently similar stars. Thedepletions are large in a majority of them, far in excess of thepredictions of the standard stellar evolution models. In order toexplore whether the large spread in Li abundances observed in giants canbe interpreted in terms of mass, moderately high resolution CCD spectraof the Li I line at 6707.8 Ä have been obtained in 65 subgiants,giants and supergiants and the lithium abundances derived. Theirabsolute magnitudes have been estimated from the Hipparcos data.Absolute magnitudes have also been determined for another 802 starswhose lithium abundances are already known from the availableliterature. All these stars have been plotted on the HR diagram andcompared with the theoretical evolutionary tracks of Bressan et al.(1993) with initial masses ranging from 1 M_sun to 9 M_sun for achemical composition typical of the solar neighbourhood: X=0.70, Y=0.28,Z=0.02. The stars of low mass of this sample, (<2M_sun), span a widerange in evolution (unmixed warm subgiants and mixed giants) andtherefore, show a correspondingly wide range of Li abundances, perhapsreminiscent of the large range in abundances observed on the mainsequence. The spread is further augmented by the effects of increasingdilution and mixing as the stars evolve to the right and up the redgiant branch. Higher mass stars show a different behaviour. Many of thegiants of masses between 2.5 and 4.0 M_sun observed in the present studyhave Li abundances close to what is predicted by the standard stellarmodels. On the other hand, there are several high mass giants (>2.5M_sun) cooler than Teff = 5000 K with Li abundances as low asthose of low mass stars of similar effective temperature. There must beparameters other than mass and evolutionary status, as implied by thestandard evolution model of a star, that control its Li abundance.
| Evolution of X-ray activity and rotation on G-K giants
The recent availability of stellar parallaxes provided by the Hipparcosstar catalogue (ESA 1997) enables an accurate determination of thepositions of single field giants in a theoretical H-R diagram and areliable estimate of their masses. The present study combines these newastrometric data with previously published X-ray fluxes and rotationalvelocities. The results confirm the existence of a sharp decrease ofX-ray emission at spectral type K1 for 2.5 M_sun < M < 5 M_sungiants. The study shows that the rotational velocity of these starsreaches a minimum at the same location in the H-R diagram. However, notight relationship between X-ray luminosities and projected equatorialvelocities was found among the sample stars. I suggest that theseresults could reflect the importance of differential rotation indetermining the level of coronal emission among >= 2.5Msun G and K giants. The restoration of rigid rotation at thebottom of the red giant branch could prevent the maintenance of largescale magnetic fields, thus explaining the sharp decrease of coronalX-ray emission at spectral type K1.
| Far-Ultraviolet Continuum of G-Type Stars: A Signature of the Temperature Minimum Region
The main results of a program of systematic comparison between observedand computed UV spectral energy distributions of field G-type stars areillustrated. We constructed the UV observed energy distributions for 53G stars, starting from the IUE Uniform Low Dispersion Archive (ULDA) andcomputed the corresponding theoretical fluxes by using the atmosphericparameters from the Catalogue of [Fe/H] Determinations (1996 edition)and a Kurucz grid of model fluxes. From the comparison betweenobservations and classical models, a UV excess shortward of 2000 Åis evident for all the program stars. The UV continuum in the region1600-2000 Å can be described by synthetic fluxes computed fromsemiempirical models based on the temperature minimum concept. Valuesfor the T_min/T_eff ratio on the order of 0.80 are suitable for theinterpretation of the observed fluxes. The residual discrepanciesshortward of 1600 Å are suggested to be effects of thechromosphere, on the basis of a comparison with the Maltby et al.semiempirical model of the Sun.
| The ROSAT all-sky survey catalogue of optically bright late-type giants and supergiants
We present X-ray data for all late-type (A, F, G, K, M) giants andsupergiants (luminosity classes I to III-IV) listed in the Bright StarCatalogue that have been detected in the ROSAT all-sky survey.Altogether, our catalogue contains 450 entries of X-ray emitting evolvedlate-type stars, which corresponds to an average detection rate of about11.7 percent. The selection of the sample stars, the data analysis, thecriteria for an accepted match between star and X-ray source, and thedetermination of X-ray fluxes are described. Catalogue only available atCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| A catalogue of [Fe/H] determinations: 1996 edition
A fifth Edition of the Catalogue of [Fe/H] determinations is presentedherewith. It contains 5946 determinations for 3247 stars, including 751stars in 84 associations, clusters or galaxies. The literature iscomplete up to December 1995. The 700 bibliographical referencescorrespond to [Fe/H] determinations obtained from high resolutionspectroscopic observations and detailed analyses, most of them carriedout with the help of model-atmospheres. The Catalogue is made up ofthree formatted files: File 1: field stars, File 2: stars in galacticassociations and clusters, and stars in SMC, LMC, M33, File 3: numberedlist of bibliographical references The three files are only available inelectronic form at the Centre de Donnees Stellaires in Strasbourg, viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5), or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 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.
| Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
| On the link between rotation and coronal activity in evolved stars.
We analyse the behaviour of coronal activity as a function of rotationfor a large sample of single and binary evolved stars for which we haveobtained CORAVEL high precision rotational velocities. This study showsthat tidal effects play a direct role in determining the X-ray activitylevel in binary evolved stars. The circularisation of the orbit is anecessary property for enhanced coronal activity in evolved binarystars.
| ROSAT X-ray observations of late-type evolved stars: On the relationship between coronal temperatures and luminosities
We present ROSAT Position Sensitive Proportional Counters (PSPC) X-rayobservations of three near-solar-mass stars, in different evolutionaryphases beyond the main sequence: eta Sco (F3 III-IV), iota Vir (F6 III),and HD 74772 (G5 III). All three of these nearby, presumably singlestars have been detected, and we have collected enough counts to performa detailed analysis of their soft X-ray spectra. While the X-ray spectraof eta Sco and HD 74772 can be fitted with Raymond-Smith thermal modelswith temperatures around 2 x 106 K, the high signal-to-noisespectrum of iota Vir provides unambiguous evidence of a multitemperatureplasma, with a two-temperature best-fit model with components atapproximately 2 x 106 K and 8 x 106 K. Evidence ofsome hot plasma (T approximately 107 K) has been also foundfor HD 74772. The present data, compared with spectral fitting resultsfor other late-type stars observed with the Einstein Observatory,indicate that the low X-ray luminosity giants (Lx is lessthan 5 x 1028 ergs/s) do not share with the higher X-rayluminosity stars of the same class the property of having substantialamount of 107 K plasma. Moreover, our results confirm thetrend of increasing X-ray luminosities with increasing coronaltemperatures.
| The orbits of moving clusters in the galactic dynamical models
The orbits of nine moving star clusters distinguished by Agekian andOrlov (1984) are studied in the rotationally symmetric field of theGalaxy. The three galactic models are considered: the potentials of Sala(1987), Allen and Martos (1986), Kutuzov and Osipkov (1989). In thefirst model applied to a local galactic region in the solar circlevicinity, the orbit of each star is periodic in the meridional plane.The presence of two streams of the moving clusters is assumed. Thesuperclusters of Sirius and Hyades are connected with these streams. Forthe two latter global galactic models, the orbits of principal stars inthe moving clusters, as well as the ones of the stars which are probablenon-members of clusters are calculated. A typical lifetime of the movingclusters in the galactic field is estimated.
| Chromospheric Activity in Galactic Open Clusters
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993ApJ...417..157B&db_key=AST
| Evolved GK stars near the sun. I - The old disk population
A sample of nearly two thousand GK giants with intermediate band, (R,I),DDO and Geneva photometry has been assembled. Astrometric data is alsoavailable for most of the stars. The some 800 members of the old diskpopulation in the sample yield accurate luminosities (from two sources),reddening values and chemical abundances from calibrations of thephotometric parameters. Less than one percent of the objects arepeculiar in the sense that the flux distribution is abnormal. Thepeculiarity is signaled by strong CH (and Ba II) and weak CH. The CH+stars are all spectroscopic binaries, probably with white dwarfcompanions, whereas the CH- stars are not. A broad absorption band,centered near 3500 A, is found in the CH+ stars whereas the CH- objectshave a broad emission feature in the same region. The intensity of theseabsorptions and emissions are independent of the intensity of abnormalspectral features. Ten percent of the old disk sample have a heavyelement abundance from one and a half to three times the solar value.The distribution of the heavy element abundances is nearly a normal onewith a peak near solar abundance and ranges three times to one sixthsolar. The distribution of the (U, V) velocities is independent of theheavy element abundance and does not appear to be random. Ten percent ofthe old disk stars show a CN anomaly, equally divided between CN strongand CN weak. Several stars of individual astrometric or astrophysicalimportance are isolated.
| Spectroscopic investigation of cool giants and the authenticity of their reported microwave emission
Surface velocities and metal abundances for 19 red giant stars in thespectral range G5 to M3 are derived on the basis of AAT echellespectroscopy data. Attention is given to the question of whether thestars reported to emit radio bursts had different physical properties(rotation rate, macroturbulence, microturbulence, and metal abundance)from those without the radio bursts, which might explain why they wereradio emitters. The various velocities had values consistent with thosepreviously found for other similar stars. There was an observed increasein both macroturbulent and, less definitely, microturbulent velocitieswith lateness of spectral type at K3 and later. A weak correlationbetween surface velocities and 8.4-GHz radio surface fluxes was found.No connection between iron abundances and radio surface fluxes wasdetected. It is concluded that few, if any, of the cool giants are radioemitters.
| Non-thermal radio emission from post-main-sequence stars
The Australia Telescope Compact Array (ATCA) has been used to make4.8-GHz observations of 24 fields containing post-main-sequence stars.These stars were selected from a sample of late-type (spectral types G,K and M) giants and bright giants within 30 pc claimed by Slee et al.,from observations with the Parkes radio telescope, to be variablenon-thermal radio emitters. No significant 4.8-GHz radio emission wasdetected from these stars. Non-detection of any stars with the ATCA isan improbable result, and calls for a re-analysis of the original Parkes8.4-GHz observations. A re-analysis suggests that the majority of theclaimed Parkes detections with S less than about 8 mJy are false. Thefive claimed Parkes detections with S greater than 8 mJy are discussedindividually on the basis of the ATCA and Molonglo Observatory SynthesisTelescope (MOST) observations. It is concluded that the Parkes, ATCA,and MOST observations do not invalidate the concept of a 'coronalboundary line' between stars exhibiting chromospheric and coronalemission, and more evolved stars displaying only cool winds.
| Search for Vega-like nearby stars with 12 micron excess
The identification of Vega-like main-sequence stars with 10-micronexcess would permit important measurements of the spatial extent of theradiating material with ground-based telescopes. In fact, 55 of the 548nearby A, F, G, and K dwarfs with IRAS catalog magnitudes at 12 micronsappear to have excess 12-micron flux. However, for only two of thesestars, Beta Pic and Zeta Lep, was it possible, using small-aperturephotometry at 2.2 and 10 microns, to verify that the 12-micron excess iswith high likelihood associated with the star. For the remaining starsthe apparent 12-micron color of the 106 A, F, G, and K stars in theobserving program is only 0.02 mag. Excess flux due to a Vega-like cloudwhich may surround some of the sources in the observing program, likeAlpha Lyrae, is thus typically not detectable at 10 microns.
| Einstein Observatory magnitude-limited X-ray survey of late-type giant and supergiant stars
Results are presented of an extensive X-ray survey of 380 giant andsupergiant stars of spectral types from F to M, carried out with theEinstein Observatory. It was found that the observed F giants orsubgiants (slightly evolved stars with a mass M less than about 2 solarmasses) are X-ray emitters at the same level of main-sequence stars ofsimilar spectral type. The G giants show a range of emissions more than3 orders of magnitude wide; some single G giants exist with X-rayluminosities comparable to RS CVn systems, while some nearby large Ggiants have upper limits on the X-ray emission below typical solarvalues. The K giants have an observed X-ray emission level significantlylower than F and F giants. None of the 29 M giants were detected, exceptfor one spectroscopic binary.
| BVRI photometry of the Gliese Catalogue stars
Photoelectri BVRI photometry on the Cousins (Kron-Cape) system has beenobtained for many of the southern faint stars in the Gliese Catalog(1969). This extends the work of Cousins (1980) and provides a uniformset of data for the nearby stars. Several red dwarfs are noted, whichwere used to define the red end of the Cousins system.
| Large and kinematically unbiased samples of G- and K-type stars. IV - Evolved stars of the old disk population
Modified Stromgren and (R,I) photometry, along with DDO and Genevaphotometry, are presented for a complete sample of evolved old-disk Gand K giants in the Bright Star Catalogue. Stars with ages of between1.5 x 10 to the 9th and 10 to the 10th yr are found to have anear-normal distribution of heavy element abundances, centered on anFe/H abundance ratio of -0.1 dex. The old disk clusters NGC 3680 and IC4651 contain red-straggler young-disk giants that are probablycontemporaries of the blue stragglers in the clusters.
| Large and kinematically unbiased samples of G- and K-type stars. II - Observations of evolved stars in the Bright Star sample. III - Evolved young disk stars in the Bright Star sample
Four color and RI observations were obtained for a large sample ofG-type and K-type stars in the Bright Star Catalogue. Data are firstpresented for 110 evolved stars. Photometry of evolved young diskpopulation stars have then been calibrated for luminosity, reddening,and metallicity on the basis of results for members of the Hyades andSirius superclusters. New DDO results are given for 120 stars.
| Activity in a Complete Sample of Red Giants
Not Available
| A microwave survey of southern red giants
The Parkes 64-m telescope has been used to survey a complete sample ofnearby red giants. The sample consisted of all 82 stars within 30 pc inthe Bright Star Catalogue having spectral types G, K, M and luminosityclasses I, II, III and occurring south of the celestial equator.Twenty-four stars, consisting of 19 G or K giants, two G or K brightgiants (luminosity class II) and three of the five M-type giants weredetected in the sample. The emitted 8.4-GHz power and surface fluxdistributions of the 24 detections have medians two orders of magnitudelower than those of the active radio emitters in close binaries andother rapidly rotating single stars. It is shown that the field redgiants with their low rotation velocities probably fit into thesurface-flux/rotation-velocity relation derived for the faster rotators.
| The Perkins catalog of revised MK types for the cooler stars
A catalog is presented listing the spectral types of the G, K, M, and Sstars that have been classified at the Perkins Observatory in therevised MK system. Extensive comparisons have been made to ensureconsistency between the MK spectral types of stars in the Northern andSouthern Hemispheres. Different classification spectrograms have beengradually improved in spite of some inherent limitations. In thecatalog, the full subclasses used are the following: G0, G5, G8, K0, K1,K2, K3, K4, K5, M0, M1, M2, M3, M4, M5, M6, M7, and M8. Theirregularities are the price paid for keeping the general scheme of theoriginal Henry Draper classification.
| A photometric survey of the bright southern Be stars
Repeated UBV photometric measurements were made of the 86 bright Bestars south of declination -20 deg, and a network of comparison starswas set up. From a statistical study of the differential photometry itwas found that short- or intermediate-term variability seems to beoccurring in about half of the Be stars, and to be more evident in thestars of earlier spectral type. It was also possible to identify 11individual short- or intermediate-term variables. Four of these (all ofearly B spectral type) appear to exhibit significant variability on atime-scale of a day or less. More intensive observations of one of thesestars, 28 Omega CMA, indicate short-term variations consistent with thepublished spectroscopic period of 1.37 day.
|
Добавить новую статью
Внешние ссылки
- - Внешних ссылок не найдено -
Добавить внешнюю ссылку
Группы:
|
Наблюдательные данные и астрометрия
| Созвездие: | Паруса |
| Прямое восхождение: | 08h44m24.00s |
| Склонение: | -42°38'57.0" |
| Видимая звёздная величина: | 4.07 |
| Расстояние: | 70.077 парсек |
| Собственное движение RA: | -24.4 |
| Собственное движение Dec: | 19 |
| B-T magnitude: | 5.135 |
| V-T magnitude: | 4.143 |
Каталоги и обозначения:
|
