Contingut
Imatges
Carregar la teva Imatge
DSS Images Other Images
Articles Relacionats
The Origins and Evolutionary Status of B Stars Found Far from the Galactic Plane. II. Kinematics and Full Sample Analysis
This paper continues the analysis of faint high-latitude B stars fromMartin. Here we analyze the kinematics of the stars and combine themwith the abundance information from the first paper to classify eachone. The sample contains 31 Population I runaways, 15 old evolved stars(including 5 blue horizontal-branch [BHB] stars, 3 post-HB stars, 1pulsating helium dwarf, and 6 stars of ambiguous classification), 1 Fdwarf, and 2 stars that do not easily fit in one of the othercategories. No star in the sample unambiguously shows thecharacteristics of a young massive star formed in situ in the halo. Thetwo unclassified stars are probably extreme Population I runaways. Thelow binary frequency and rotational velocity distribution of thePopulation I runaways imply that most were ejected from dense starclusters by the dynamic ejection scenario. However, we remain puzzled bythe lack of runaway Be stars. We also confirm that PB 166 and HIP 41979are both nearby solar-metallicity BHB stars.Based on observations made at the 2.1 m Otto Struve Telescope ofMcDonald Observatory, operated by the University of Texas at Austin.
| Rotational Velocities of B, A, and Early-F Narrow-lined Stars
Projected rotational velocities for 58 B, A, and early-F stars have beendetermined from high-resolution spectroscopic observations made at KittPeak National Observatory with the coudé feed telescope. All thestars are slowly rotating with vsini<60 km s-1. Because oftheir low rotational velocities, 15 of the stars have been observed asprospective, early-type, radial velocity standards.
| Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i
This work is the second part of the set of measurements of v sin i forA-type stars, begun by Royer et al. (\cite{Ror_02a}). Spectra of 249 B8to F2-type stars brighter than V=7 have been collected at Observatoirede Haute-Provence (OHP). Fourier transforms of several line profiles inthe range 4200-4600 Å are used to derive v sin i from thefrequency of the first zero. Statistical analysis of the sampleindicates that measurement error mainly depends on v sin i and thisrelative error of the rotational velocity is found to be about 5% onaverage. The systematic shift with respect to standard values fromSlettebak et al. (\cite{Slk_75}), previously found in the first paper,is here confirmed. Comparisons with data from the literature agree withour findings: v sin i values from Slettebak et al. are underestimatedand the relation between both scales follows a linear law ensuremath vsin inew = 1.03 v sin iold+7.7. Finally, thesedata are combined with those from the previous paper (Royer et al.\cite{Ror_02a}), together with the catalogue of Abt & Morrell(\cite{AbtMol95}). The resulting sample includes some 2150 stars withhomogenized rotational velocities. Based on observations made atObservatoire de Haute Provence (CNRS), France. Tables \ref{results} and\ref{merging} 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/393/897
| 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
| 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
| Spectroscopy of Hot Stars in the Galactic Halo. II. The Identification and Classification of Horizontal-Branch and Other A-Type Stars
We discuss a spectroscopic and photometric technique that enables theidentification and classification of field horizontal-branch (FHB) andother A-type stars, even from relatively low signal-to-noise ratiomedium-resolution spectra. This technique makes use of broadband UBVcolors predicted from model atmosphere calculations and Balmer lineprofiles and Ca II K equivalent widths determined from synthetic spectrato estimate the physical parameters T_eff, log g, and [Fe/H] for starsin the effective temperature range 6000-10,000 K. A comparison of ourmethod with high signal-to-noise ratio spectra of standard starsindicates a scatter in the derived parameters of sigma(T_eff)=+/-250 K,sigma(log g)=+/-0.14 dex, and sigma([Fe/H])=+/-0.12 dex. This precisionallows for a separation of low surface gravity FHB and other, generallyhigher surface gravity, A-type (and somewhat later) stars. We alsodevelop a synthetic-template comparison technique, which is veryeffective in the identification of metallic-line and peculiar A-typestars. A detailed investigation of the influence of noise in the spectraon the determination of physical parameters shows that, for spectra withsignal-to-noise ratios in the range 10
| Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS
Radial velocities have been determined for a sample of 2930 B2-F5 stars,95% observed by the Hipparcos satellite in the north hemisphere and 80%without reliable radial velocity up to now. Observations were obtainedat the Observatoire de Haute Provence with a dispersion of 80Ä,mm(-1) with the aim of studying stellar and galactic dynamics.Radial velocities have been measured by correlation with templates ofthe same spectral class. The mean obtained precision is 3.0 km s(-1)with three observations. A new MK spectral classification is estimatedfor all stars. Based on observations made at the Haute ProvenceObservatory, France and on data from The Hipparcos Catalogue, ESA.Tables 4, 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr or viahttp://cdsweb.u-strasbg.fr/Abstract.htm
| The nature of the sharp-lined A1V star HD 72660
In order to specify the nature of the sharp-lined A1V star HD 72660, itseffective temperature and surface gravity have been determined using twodifferent methods. First, the ultraviolet energy distribution of HD72660 has been compared with that of the normal A0 star HD 10939 andwith the predictions of two model atmospheres. Secondly, the parametershave been derived from Moon & Dworetsky's (1985) calibration of uvbycolors. Both methods yield consistent values Teff = 9750 +/-\200 K, logg = 4.00 +/-\ 0.20 dex. In a second part, high resolution highsignal to noise optical spectra centered on <~mbda4500 Angstroms,<~mbda5080 Angstroms and <~mbda6160 Angstroms have beensynthesized using Gray's (1995) and Takeda's (1995) LTE codes. Theabundances of 13 elements were derived. C and O are found to beunderabundant with respect to the solar value (-0.60 and -0.52 dexrespectively) whereas Ti, Cr, Fe, Ni are overabundant (between +0.37 and+0.72 dex). Ca appears to be moderately overabundant (+0.16 dex). Theseresults suggest that HD 72660 is a hot Am star. Based on observationscollected at Observatoire de Haute Provence (France)
| 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
| The Consistency of Stromgren-Beta Photometry for Northern Galactic Clusters. II. Praesepe and NGC 752
We have measured stars in Praesepe and NGC 752 in aninternally-consistent Stromgren-Beta system. This system is based inlarge part on published Hyades and Coma measurements. On comparing ourPraesepe results to those of Crawford and Barnes (1969, AJ, 74, 818), wefind that the published color indices require corrections of 10-18 mmagto put them on the Hyades-Coma system. This deduction applies for b-y,m_1 and Beta (but not c_1). For the NGC 752 data of Crawford and Barnes(1970, AJ, 75, 946), we obtain a nonzero correction only for Beta. Thiscorrection is about 9 mmag. Also for NGC 752, we find that the data ofTwarog (1983, ApJ, 267, 207) require corrections ranging from 4-17 mmag,with all Stromgren indices being affected and the largest correctionbeing for m_1. These corrections resolve the long-standing problem posedby the differences between the Twarog and Crawford-Barnes data. Forthree published sources of V magnitudes, we obtain offsets ranging from-14 to +27 mmag relative to our zero point, and we suggest that suchoffsets are fairly common in published photometry for galactic clusters.For Praesepe, we use new and corrected data to test for a c_1 anomalyand is indistinguishable from Coma in that regard. (SECTION: StellarClusters and Associations)
| The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJS...99..135A&db_key=AST
| 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.
| Compositional differences among the A-type stars. 2: Spectrum synthesis up to V sin i = 110 km/s
The results of an abundance analysis of 15 early A-type stars arepresented here. These stars have u sin i on the range 6 to 109 km/s andall but one of them (an Am star) are classified as normal. Reliableabundances (uncertainties about a quarter dex or less) are obtained fortwelve elements. Considerable star-to-star abundance variations arepresent among both the narrow lined and broader lined stars. Mostelements have abundances which scale with those of iron. Carbon andcalcium are interesting exceptions. Carbon abundances seem to beanti-correlated with those of iron, while calcium abundances may exhibita more complex behavior. Heavy elements seem enhanced for most stars.
| A ROSAT Survey of Hot DA White Dwarfs in Non-Interacting Binary Systems
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994MNRAS.270..499B&db_key=AST
| The Spacelab-1 Very Wide Field Survey of UV-excess objects. IV. The performance of the instrument in combination with optical photometry as a means of identifying stars with peculiar properties.
UV (195 nm) and Stroemgren uvby photometry of a 110 square degree fieldat high southern galactic latitudes are analyzed through a comparison ofi) UV magnitudes for 57 stars of various types common to the publishedTD1 catalogue and the Very Wide Field Camera (VWFC); and ii) observedand theoretical two-colour diagrams. The higher sensitivity of the VWFC(=~0.5magnitude) and its more complete survey are exemplified by thedetection and UV measurement of a series of objects with moderateUV-excess in addition to detection of some very blue objects of variousnature down to fainter than 12th magnitude in the optical domain. Adeeper survey with a VWFC-type instrument could provide a completesample for studies of the group properties of faint blue stars. Duringthe uvby reductions it was found that the usual procedure of plottingresiduals as functions of declination, hour angle and airmass can be apowerful and diagnostic test of photometer rigidity.
| Compositional Differences among the A-Type Stars - Part One - Six Narrowlined Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...276..142H&db_key=AST
| The consistency of Stromgren-beta photometry for northern galactic clusters. I - The Hyades and Coma
We have compared the Hyades, Coma, and a set of field standard stars inthe V and Stromgren-beta systems. If Stromgren data by Crawford and hiscollaborators (1966, 1969, 1970) are considered, all the data turn outto be on the same system; no corrections as large as several mmag arerequired to achieve this state. For beta, similar consistency betweenthe Hyades and Coma is already known to exist. We find that for thestandard stars, beta values from the literature are consistent with theHyades-Coma system. For V, we adopt corrections derived previously byJoner and Taylor (1990) for published cluster photometry. Given thesecorrections, we find that within rather generous accidental-errorlimits, the V systems for the field stars and the clusters agree.
| Average Profiles and Equivalent Widths of Hydrogen Lines of 76 Normal and Peculiar Stars - Masses and Radii of Studied Stars
Not Available
| Metallic line profiles of the AO V star VEGA
High dispersion ultrahigh signal to noise Reticon spectra of Vega wereobtained with the coude spectrograph of the 1.2 m telescope. A meansignal to noise ratio of 2500 over the spectral region lambdas from 3825to 5435 was achieved. Examination of the line profiles confirmed thepresence of two different types of profiles which were previously seenin IIIaJ and lower signal to noise Reticon spectra. The profiles of thestrong lines are essentially classical rotational profiles with enhancedwings which are slightly stronger than expected while those of weaklines are clearly flat-bottomed resulting in a trapezoidal appearance. Afew possible theoretical explanations are presented.
| The measurement of precise radial velocities of early type stars
Methods are discussed which have made it possible to measure radialvelocities to within 1-3 km/s for O, B, and A spectral-type stars of allv sin i. The methods are based on the premise that neither the spectraltype nor the rotation velocity of a star need be well known prior to thevelocity measurement. This makes them particularly suitable for surveystudies or programs dealing with very heterogeneous samples of earlystars. Observations of early type members of the Pleiades and AlphaPersei open clusters at 3787 A shown that the radial-velocity zero pointused here for the early type stars is consistent with that for late-typestars to about 1 km/s for all spectral types and projected rotationvelocities.
| Anomalous infrared emitters among A-type stars
Spectroscopic observations of a sample of 26 stars have been analyzed inthe blue and near-IR to find out if anomalous IR emitters (AIEs) have aspectral signature. It is found that many, but not all, such starsexhibit shell characteristics. Analysis of available IRAS photometricobservations of A-type stars shows that the detection of circumstellarfeatures depends strongly on the number of IR bands at which the objectwas observed. Out of the 707 stars observed by IRAS, 41 AIEs, or 5.7percent, are found. Among nonsupergiant AIEs, 23 percent show shellfeatures. The true percentage of AIEs among A-type stars is estimated tobe 1.5 percent in a volume-corrected sample. A list of 24 stars whichwere apparently not previously detected as AIEs is given.
| The luminosity scale of RR Lyrae stars with the Baade-Wesselink method. I - Photometry and radial velocities
UBVRI optical and JK IR photometry and radical velocities are presentedfor a sample of 13 field RR Lyrae stars with metallicities ranging frommetal-rich to metal-poor. These stars include 11 ab-type variables, SWAnd, RR Cet, SU Dra, Rx Eri, RR Gem, RR Leo, TT Lyn, AV Peg, AR Per, TUUMa, and UU Vir, and two c-type variables, TV Boo and T Sex. Light,color, and radial velocity curves of these RR Lyrae stars are alsopresented in the paper.
| Radial-velocity measurements in 20 young open clusters
The further results of a program to determine the radial velocities ofyoung open clusters are presented. Using the KPNO coude spectrographcoupled with the 1-m feed and 2.1-m telescopes, radial velocities havebeen measured for nearly one hundred stars, most of which are ofspectral type B and A, in 20 young clusters. The combination ofinstruments and the use of cross-correlation techniques show that radialvelocities of B and A type stars as faint as 10th magnitude can bedetermined with an internal precision of less than about 2 km/s. Asexpected, the uncertainties in the velocity determination for the youngclusters are dominated by spectroscopic binary stars in these clusters.A third of the stars in the sample are found to be spectroscopicbinaries, but with a large variation in the frequency of binaries fromcluster to cluster. Because the time coverage is still limited, thisshould be considered a lower limit to the binary frequency. Clustervelocities are determined after eliminating binaries and known nonmemberstars. The new velocities are compared with a model galactic rotationcurve, as well as with previous velocity determinations.
| A catalog of bright UVBY beta standard stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1987PASP...99.1184P&db_key=AST
| A UVBY beta survey of northern-hemisphere active binaries. I - The observations
A recent detailed calibration of the uvby photometric system forlate-type stars has opened the possibility of studying photometriceffects of stellar activity in the RS CVn group of binaries. A uvby betaphotometric study of 72 northern-hemisphere binary systems with activechromospheres has been carried out at the Roque de los MuchachosObservatory (La Palma, Canary Islands) with a People's photometerattached to the JKT 1.0 m telescope. The standarized colors and Vmagnitudes are presented as a function of the orbital phase, along withan indication of their accuracy. A detailed discussion of atmosphericextinction, characteristics of the photometric system, andtransformation coefficients is also included.
| Catalogue of the energy distribution data in spectra of stars in the uniform spectrophotometric system.
Not Available
| UV photometric data on standard A, F and AM stars observed by S2/68
Data derived from the stellar UV fluxes of the S2/68 experiment andanalyzed and interpreted by Van't Veer et al. (1980) are presented.There are two tables of photometric data. One lists all standard stars,without exception, belonging to the intersection of the following threecatalogs: (1) the Thompson et al. (1978) catalog of S2/68 fluxes; (2)the PMR catalog (Philip et al., 1976), which is an analysis of theHauck-Mermilliod catalog (1975) of homogeneous four color data; and (3)the Crawford and Barnes (1970) list of standard stars for uvbyphotometry. The other table lists all the Am stars, without exception,belonging to the intersection of the following three catalogs: (1)Thompson et al. (1978); (2) PMR (1976); and (3) the Hauck (1973) catalogof the Am stars.
| Balmer-line equivalent widths in main sequence B-F stars, and comparison with model atmospheres
Equivalent widths of the Balmer H-alpha, H-beta, and H-gamma lines weremeasured for 175 main-sequence B-F stars and compared with curvescalculated from various model stellar atmospheres. When averaged overeach spectral subtype, the equivalent widths are well represented by thestandard models; this confirms the previous finding of Glushneva andDoroshenko (1980) that the models are fully consistent with theobservations.
| Spectral classification from the ultraviolet line features of S2/68 spectra. III - Early A-type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978A&AS...33...15C&db_key=AST
|
Enviar un nou article
Enllaços Relacionats
- - No s'ha trobat enllaços -
Enviar un nou enllaç
Membre dels grups següents:
|
Dades d'Observació i Astrometria
| Constel·lació: | Triangulum |
| Ascensió Recta: | 02h18m57.00s |
| Declinació: | +28°38'33.0" |
| Magnitud Aparent: | 5.03 |
| Distancia: | 107.411 parsecs |
| Moviment propi RA: | 7.2 |
| Moviment propi Dec: | 0.5 |
| B-T magnitude: | 5.316 |
| V-T magnitude: | 5.293 |
Catàlegs i designacions:
|
