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Herbig Ae/Be Stars in nearby OB Associations
We have carried out a study of the early-type stars in nearby OBassociations spanning an age range of ~3-16 Myr, with the aim ofdetermining the fraction of stars that belong to the Herbig Ae/Be class.We studied the B, A, and F stars in the nearby (<=500 pc) OBassociations Upper Scorpius, Perseus OB2, Lacerta OB1, and Orion OB1,with membership determined from Hipparcos data. We also included in ourstudy the early-type stars in the Trumpler 37 cluster, part of the CepOB2 association. We obtained spectra for 440 Hipparcos stars in theseassociations, from which we determined accurate spectral types, visualextinctions, effective temperatures, luminosities and masses, usingHipparcos photometry. Using colors corrected for reddening, we find thatthe Herbig Ae/Be stars and the classical Be (CBe) stars occupy clearlydifferent regions in the JHK diagram. Thus, we use the location on theJHK diagram, as well as the presence of emission lines and of strong 12μm flux relative to the visual, to identify the Herbig Ae/Be stars inthe associations. We find that the Herbig Ae/Be stars constitute a smallfraction of the early-type stellar population even in the youngerassociations. Comparing the data from associations with different agesand assuming that the near-infrared excess in the Herbig Ae/Be starsarises from optically thick dusty inner disks, we determined theevolution of the inner disk frequency with age. We find that the innerdisk frequency in the age range 3-10 Myr in intermediate-mass stars islower than that in the low-mass stars (<1 Msolar) inparticular, it is a factor of ~10 lower at ~3 Myr. This indicates thatthe timescales for disk evolution are much shorter in theintermediate-mass stars, which could be a consequence of more efficientmechanisms of inner disk dispersal (viscous evolution, dust growth, andsettling toward the midplane).
| Rotational Brightness Modulation and Starspots on the RS CVn-type Stars IN Com, IL Com, UX Ari, and V711 Tau
UBVRI photometric observations and models of spotting are presented forfour noneclipsing RS CVn systems: IN Com (G5III/IV), IL Com (F8V+F8V),UX Ari (K01V+G5V), and V711 Tau (K1IV+G5V). A low amplitude variabilitycaused by cold (T=1700K)spots which can occupy up to 19% of the star''ssurface is confirmed for the little-studied star IL Com. Long-term lightcurves are constructed and the stellar magnitudes and color indices ofthe unspotted photospheres are estimated for IN com, UX Ari, and V711Tau. It is shown that UX Ari becomes bluer with decreasing brightness,so its variability cannot be fully explained in terms of cold spots.Models of spotting on In Com and V711 Tau are constructed from the fullset of available photometric observations. The spots on both of thesevariables lie at middle latitudes and occupy up to 22% (In Com) and 33%(V711 Tau) of the stars'' surfaces. Both stars manifest a tendency forthe width of the spots to decrease as their area increases. This is acrude analog of the Maunder butterflies. These stars experience cyclicalspot activity and have a differential rotation of the type found on thesun.
| BV photometry of UX Ari in the period 1987-2002
We present 14.3 years of previously unpublished photometric observationsof UX Ari. The observations were obtained between1987.9 and 2002.2 using the T3 0.4-metre Automatic PhotoelectricTelescope at Fairborn Observatory and consist of 1228 B band and 1213 Vband measurements. The comparison star was 62 Ari. Wehave analyzed the new data together with previously publishedphotometric observations. The V magnitude shows variations with dominantperiods of about 12 and 25 years, where the longest period seems tocorrespond to an activity cycle. The previously reported anticorrelationbetween the B-V colour and V magnitude variations is confirmed.Tables 2 and 3 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.125.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/402/1033
| Research Note Hipparcos photometry: The least variable stars
The data known as the Hipparcos Photometry obtained with the Hipparcossatellite have been investigated to find those stars which are leastvariable. Such stars are excellent candidates to serve as standards forphotometric systems. Their spectral types suggest in which parts of theHR diagrams stars are most constant. In some cases these values stronglyindicate that previous ground based studies claiming photometricvariability are incorrect or that the level of stellar activity haschanged. Table 2 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/367/297
| Rotation and lithium in single giant stars
In the present work, we study the link between rotation and lithiumabundance in giant stars of luminosity class III, on the basis of alarge sample of 309 single stars of spectral type F, G and K. We havefound a trend for a link between the discontinuity in rotation at thespectral type G0III and the behavior of lithium abundances around thesame spectral type. The present work also shows that giant starspresenting the highest lithium contents, typically stars earlier thanG0III, are those with the highest rotation rates, pointing for adependence of lithium content on rotation, as observed for otherluminosity classes. Giant stars later than G0III present, as a rule, thelowest rotation rates and lithium contents. A large spread of about fivemagnitudes in lithium abundance is observed for the slow rotators.Finally, single giant stars with masses 1.5 < M/Msun<=2.5 show a clearest trend for a correlation between rotational velocityand lithium abundance. Based on observations collected at theObservatoire de Haute -- Provence (France) and at the European SouthernObservatory, La Silla (Chile). Table 2 is only available electronicallywith the On-Line publication athttp://link.springer.de/link/service/00230/
| Library of Medium-Resolution Fiber Optic Echelle Spectra of F, G, K, and M Field Dwarfs to Giant Stars
We present a library of Penn State Fiber Optic Echelle (FOE)observations of a sample of field stars with spectral types F to M andluminosity classes V to I. The spectral coverage is from 3800 to 10000Å with a nominal resolving power of 12,000. These spectra includemany of the spectral lines most widely used as optical and near-infraredindicators of chromospheric activity such as the Balmer lines (Hαto Hepsilon), Ca II H & K, the Mg I b triplet, Na I D_1, D_2, He ID_3, and Ca II IRT lines. There are also a large number of photosphericlines, which can also be affected by chromospheric activity, andtemperature-sensitive photospheric features such as TiO bands. Thespectra have been compiled with the goal of providing a set of standardsobserved at medium resolution. We have extensively used such data forthe study of active chromosphere stars by applying a spectralsubtraction technique. However, the data set presented here can also beutilized in a wide variety of ways ranging from radial velocitytemplates to study of variable stars and stellar population synthesis.This library can also be used for spectral classification purposes anddetermination of atmospheric parameters (T_eff, logg, [Fe/H]). A digitalversion of all the fully reduced spectra is available via ftp and theWorld Wide Web (WWW) in FITS format.
| A HIPPARCOS Census of the Nearby OB Associations
A comprehensive census of the stellar content of the OB associationswithin 1 kpc from the Sun is presented, based on Hipparcos positions,proper motions, and parallaxes. It is a key part of a long-term projectto study the formation, structure, and evolution of nearby young stellargroups and related star-forming regions. OB associations are unbound``moving groups,'' which can be detected kinematically because of theirsmall internal velocity dispersion. The nearby associations have a largeextent on the sky, which traditionally has limited astrometricmembership determination to bright stars (V<~6 mag), with spectraltypes earlier than ~B5. The Hipparcos measurements allow a majorimprovement in this situation. Moving groups are identified in theHipparcos Catalog by combining de Bruijne's refurbished convergent pointmethod with the ``Spaghetti method'' of Hoogerwerf & Aguilar.Astrometric members are listed for 12 young stellar groups, out to adistance of ~650 pc. These are the three subgroups Upper Scorpius, UpperCentaurus Lupus, and Lower Centaurus Crux of Sco OB2, as well as VelOB2, Tr 10, Col 121, Per OB2, alpha Persei (Per OB3), Cas-Tau, Lac OB1,Cep OB2, and a new group in Cepheus, designated as Cep OB6. Theselection procedure corrects the list of previously known astrometricand photometric B- and A-type members in these groups and identifiesmany new members, including a significant number of F stars, as well asevolved stars, e.g., the Wolf-Rayet stars gamma^2 Vel (WR 11) in Vel OB2and EZ CMa (WR 6) in Col 121, and the classical Cepheid delta Cep in CepOB6. Membership probabilities are given for all selected stars. MonteCarlo simulations are used to estimate the expected number of interloperfield stars. In the nearest associations, notably in Sco OB2, thelater-type members include T Tauri objects and other stars in the finalpre-main-sequence phase. This provides a firm link between the classicalhigh-mass stellar content and ongoing low-mass star formation. Detailedstudies of these 12 groups, and their relation to the surroundinginterstellar medium, will be presented elsewhere. Astrometric evidencefor moving groups in the fields of R CrA, CMa OB1, Mon OB1, Ori OB1, CamOB1, Cep OB3, Cep OB4, Cyg OB4, Cyg OB7, and Sct OB2, is inconclusive.OB associations do exist in many of these regions, but they are eitherat distances beyond ~500 pc where the Hipparcos parallaxes are oflimited use, or they have unfavorable kinematics, so that the groupproper motion does not distinguish it from the field stars in theGalactic disk. The mean distances of the well-established groups aresystematically smaller than the pre-Hipparcos photometric estimates.While part of this may be caused by the improved membership lists, arecalibration of the upper main sequence in the Hertzsprung-Russelldiagram may be called for. The mean motions display a systematicpattern, which is discussed in relation to the Gould Belt. Six of the 12detected moving groups do not appear in the classical list of nearby OBassociations. This is sometimes caused by the absence of O stars, but inother cases a previously known open cluster turns out to be (part of) anextended OB association. The number of unbound young stellar groups inthe solar neighborhood may be significantly larger than thoughtpreviously.
| 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
| Catalogs of temperatures and [Fe/H] averages for evolved G and K stars
A catalog of mean values of [Fe/H] for evolved G and K stars isdescribed. The zero point for the catalog entries has been establishedby using differential analyses. Literature sources for those entries areincluded in the catalog. The mean values are given with rms errors andnumbers of degrees of freedom, and a simple example of the use of thesestatistical data is given. For a number of the stars with entries in thecatalog, temperatures have been determined. A separate catalogcontaining those data is briefly described. Catalog only available atthe CDS 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
| BVR Photometry of the Three RS CVn Binary Stars: V711 Tau, UX Ari and IM Peg
Not Available
| The photoelectric astrolabe catalogue of Yunnan Observatory (YPAC).
The positions of 53 FK5, 70 FK5 Extension and 486 GC stars are given forthe equator and equinox J2000.0 and for the mean observation epoch ofeach star. They are determined with the photoelectric astrolabe ofYunnan Observatory. The internal mean errors in right ascension anddeclination are +/- 0.046" and +/- 0.059", respectively. The meanobservation epoch is 1989.51.
| The gas flows of SU Aurigae.
Series of high-resolution echelle spectra of the T Tauri star SU Aurigaewere collected during 3 observing periods. Simultaneous photoelectricUBV photometry was made during one period. We have analysed selectedspectral orders, covering the Balmer lines from Hα to Hδ, HeI 5876A, the Na I D lines and Ca II 8662A in addition to a number ofphotospheric absorption lines. We confirm and extend the results foundin two similar studies by Giampapa et al. (1993ApJS...89..321G) andJohns & Basri (1995ApJ...449..341J & 1995AJ....109.2800J).Features which have been persistent over the years are the simultaneousoccurrence of mass infall and outflow in the line-of-sight to the star.The outflow is seen as blueshifted absorption components in Hα andHβ, but not in the higher Balmer lines. The inflow is most evidentthrough the redshifted absorption components in the differentialprofiles (SU Aur minus standard) of Hβ and the higher Balmer lines,while there is also a redshifted absorption-like component superimposedon the red wing of the Hα emission. This indicates an outflow ofgas in the outer part of the circumstellar envelope/wind of the star anda simultaneous inflow/accretion in the innermost region of the envelope.No free-fall acceleration of the inflowing gas was found from measuredaccretion component velocities from Hα to Hδ. We foundvariations of the inflow velocity with an amplitude of about 50km/s on atime-scale of 3 days, similar to the period found earlier in theintensity variations of Hα and Hβ. There is a correlationbetween the variability of the He I 5876A absorption line intensity andthe variability in intensity of the redshifted Balmer absorption lines.This indicates that the He I line formation is dependent on theaccretion. We identify the periodic variations with modulation of theprojected inflow velocity by the stellar rotation and find that a modelwith magnetically channeled accretion in a dipole field inclined to theaxis of stellar rotation describes the observations in a natural way. SUAur is seen almost edge on. The time-scale of variability in theHα blueshifted absorptions at radial velocities of -100 to-200km/s is less than one day. This implies a stellar wind accelerationregion within 3 stellar radii and we find that the wind deceleratesoutside this region. The process of outflow is not steady but ratherimpulsive, which may result in the formation of expanding shells. Thetraces of such decelerated shells at large distance from the star areobserved as a more stable blueshifted absorption at about -50km/s in theprofiles of the Hα and Na I D-lines. During one period we observeda very strong event of mass ejection where the material was seen todecelerate over 3 days. We have also made surface (Doppler) imaging ofthe stellar surface using photospheric Fe I line profiles, which arevariable in intensity and indicate the presence of stellar surfacetemperature inhomogeneities. The simultaneous UBV photometry providesconstraints on such modeling, although due to the lack of data we do notinclude the photometry in the temperature mapping procedure. However,the derived temperature map is consistent with the lack of rotationallymodulated variability in the B-V photometry.
| Correlations between the flaring radio emission and starspot distribution of UX ARIETIS
We have observed UX Arietis at C band (6 cm) for 3 weeks with four VeryLong Array (VLA) antennas. The temporal coverage during the program wasapproximately three scans per day. A few days into the VLA program, UXAri began a radio flaring period which lasted for at least 2 weeks. Allthe radio fluxes were above the system noise during this episode, butthe largest values (up to 270 mJy) occurred close to 0.0 phase. Thisphasing is confirmed by the UX Ari radio observations of Neidhofer,Massi & Chiuderi-Drago (1993). Visible-band light curves of UX Ariwere obtained both during and after our radio observations; thepeak-to-peak variation in all filters was approximately equal to 0.2mag. The light curves indicate that the maximum starspot visibilityoccurred very close to 0.0 phase, the same phase as the radio maxima.Closer comparison of our radio and optical light curves indicates thatthey are almost perfectly anticorrelated. A similar radio/opticalcorrelation has been found by Lim et al (1992) and Lim et al (1994) forthe single KO V star and AB Dor. We make the following conclusions fromour observations. First, the episodes of long-term (approximately hoursto days) radio flaring were modulated by stellar eclipes. Second, theflares were located close to the starspot groups. Third, the sizes werecompared to sized of the starspot groups, which is consistent withnonthermal emission of brightness temperature Tbapproximately 1010-13 K. Fourth, the radio emission aroseonly from the midlatitude starspot groups. Last, the radio flaresemitted their radiation nearly normal to the stellar surface.
| 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.
| BV photometry and Hα spectroscopy of the RS Canum Venaticorum binary UX Arietis.
We present differential BV photometry of UX Ari obtained on 76 nightsduring 1989-94 and Hα spectroscopy obtained on 14 nights duringthe 1990-91 observing season. The migration of the phase of lightminimum indicates a life-time longer than 20 years for the starspotslocated at synchronous latitudes and a life-time in the range 2-8 yearsfor those located at faster rotating latitudes. UX Ari is bluer at lightminimum than at light maximum. We interpret this as due to an increasein the fractional contribution in the blue spectral region from thehotter secondary as the cool active star becomes faint. The amplitudeshows a modulation with a period around 10-13 years, apparentlyanticorrelated with the brightness at light minimum. Lower amplitudesoccur when the spots are more evenly distributed longitudinally ratherthan when the levels of spot activity are less. The mean brightness alsovaries, but with a time-scale longer than 20 years. The Hαemission equivalent width does not show any significant phasemodulation. The measured Hα equivalent widths of both componentsare, most likely, affected by variations in their relative continuumlevels as the active star varies.
| Dust emission features in 3-micron spectra of Herbig Ae/Be stars
Attention is given to low- and medium-resolution spectra in the 3-micronregion of 24 Herbig Ae/Be stars obtained in a search for organicfeatures from the dust around young stars. The 3.29-micron emissionfeature from aromatic hydrocarbons was detected in three objects: LkH-alpha 25, XY Per, and AS 310. Two other stars, HD 245185 and HK Ori,may have weak features. About 20 percent of the Herbig Ae/Be surveyed todate have firmly detected 3.29-micron features. The available dataindicate that the 3.29-micron feature is more extended around HerbigAe/Be stars of earlier spectral type, possibly due to dehydrogenizationor destruction of the aromatics near these stars. It is suggested thatthe total number of aromatics excited by the stars is also greateraround the earlier-type objects.
| The correction in right ascension of 508 stars determinated with PMO photoelectric transit instrument.
Not Available
| High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances
A high-resolution spectroscopic survey of 671 G and K field giants isdescribed. Broad-band Johnson colors have been calibrated againstrecent, accurate effective temperature, T(eff), measurements for starsin the range 3900-6000 K. A table of polynomial coefficients for 10color-T(eff) relations is presented. Stellar atmosphere parameters,including T(eff), log g, Fe/H, and microturbulent velocity, are computedfor each star, using the high-resolution spectra and various publishedphotometric catalogs. For each star, elemental abundances for a varietyof species have been computed using a LTE spectrum synthesis program andthe adopted atmosphere parameters.
| Large and Kinematically Unbiased Samples of G- and K-Type Stars. III. Evolved Young Disk Stars in the Bright Star Sample
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1989PASP..101...54E&db_key=AST
| 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.
| BV photometry of UX ARIETIS
Differential BV photometry of UX Ari obtained on 58 nights during1984-1985, 1985-1986, 1986-1987, and 1987-1988 observing season ispresented. It is found that (B-V) is phase dependent, with the systembeing reddest at the light maximum. This is interpreted as being due tothe variable fractional contribution by the G5 V component to the totallight at shorter wavelengths. An analysis of the available dataindicates that, at larger amplitudes of the photometric wave, thebrightness at maximum increases and that at minimum decreases, and bothconverge to DeltaV of about 1.0 mag at very low amplitudes. It impliesthat the low wave amplitudes are essentially due to more homogeneity inthe surface distribution of spots rather than to low levels of spotactivity. The variation in wave amplitude is found to be near-sinusoidalwith a period around 13-14 years.
| A search for lithium-rich giant stars
Lithium abundances or upper limits have been determined for 644 brightG-K giant stars selected from the DDO photometric catalog. Two of thesegiants possess surface lithium abundances approaching the 'cosmic' valueof the interstellar medium and young main-sequence stars, and eight moregiants have Li contents far in excess of standard predictions. At leastsome of these Li-rich giants are shown to be evolved to the stage ofhaving convectively mixed envelopes, either from the direct evidence oflow surface carbon isotope ratios, or from the indirect evidence oftheir H-R diagram positions. Suggestions are given for the uniqueconditions that might have allowed these stars to produce or accrete newlithium for their surface layers, or simply to preserve from destructiontheir initial lithium contents. The lithium abundance of the remainingstars demonstrates that giants only very rarely meet the expectations ofstandard first dredge-up theories; the average extra Li destructionrequired is about 1.5 dex. The evolutionary states of these giants andtheir average masses are discussed briefly, and the Li distribution ofthe giants is compared to predictions of Galactic chemical evolution.
| Photometric variability in chromospherically active stars. III - The binary stars
Differential UBV photometry of 49 late-type chromospherically activebinary stars has been obtained. A total of 12,353 differential UBVmagnitudes have been acquired and are used to determine seasonalphotometric periods, amplitudes, mean brightnesses, maximum spotamplitudes, 'unspotted' differential magnitudes, and times of minimumlight. Standard Fourier techniques are used to investigate the cause ofthe light variability. Eight stars are found which exhibit lightvariations due not to spot activity but rather to ellipticity and/orreflection effect. Others show combinations of all three effects. Someof the systems also show substantial differences between theirrotational and orbital period.
| The rotational break for G giants
New high-resolution spectroscopic observations have been obtained for 73G giants. Fourier analysis of their spectral lines yields rotationvelocities and macroturbulence dispersions. Combined with data from anearlier study, total of 86 analyses of luminosity class III giants isnow available. The existence of a rotational discontinuity forluminosity class III giants is confirmed, but it is found to be near G0III rather than G5 III, as indicated in the earlier work. Evidence forrotation being a single-valued function of spectral type isstrengthened. The observations are interpreted in terms of adynamo-generated magnetic brake and a 'rotostat' phenomenon.
| 1985/86 Photometry of the RS CVn Binary UX Arietis
Not Available
| Autumn 1981 Photoelectric Observations of the Starspot Activity on UX Arietis
Not Available
| Final catalogue of 229 photometric standards in UBV system near the selected areas 1-115
Not Available
| 1974-75 UBV photometry of the radio binary UX Ari.
Not Available
| UBV and JHKL photometry of the radio star UX Ari = HD 21242
Not Available
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