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An Overview of the Rotational Behavior of Metal-poor Stars
This paper describes the behavior of the rotational velocity inmetal-poor stars ([Fe/H] <= -0.5 dex) in different evolutionarystages, based on vsin i values from the literature. Our sample iscomprised of stars in the field and some Galactic globular clusters,including stars on the main sequence, the red giant branch (RGB), andthe horizontal branch (HB). The metal-poor stars are, mainly, slowrotators, and their vsin i distribution along the HR diagram is quitehomogeneous. Nevertheless, a few moderate to high values of vsin i arefound in stars located on the main sequence and the HB. We show that theoverall distribution of vsin i values is basically independent ofmetallicity for the stars in our sample. In particular, thefast-rotating main sequence stars in our sample present rotation ratessimilar to their metal-rich counterparts, suggesting that some of themmay actually be fairly young, in spite of their low metallicity, or elsethat at least some of them would be better classified as blue stragglerstars. We do not find significant evidence of evolution in vsin i valuesas a function of position on the RGB; in particular, we do not confirmprevious suggestions that stars close to the RGB tip rotate faster thantheir less-evolved counterparts. While the presence of fast rotatorsamong moderately cool blue HB stars has been suggested to be due toangular momentum transport from a stellar core that has retainedsignificant angular momentum during its prior evolution, we find thatany such transport mechanisms most likely operate very fast as the stararrives on the zero-age HB (ZAHB), since we do not find a link betweenevolution off the ZAHB and vsin i values. We present an extensivetabulation of all quantities discussed in this paper, including rotationvelocities, temperatures, gravities, and metallicities [Fe/H], as wellas broadband magnitudes and colors.
| Do the Nearby Blue Horizontal Branch Stars Belong to the Thick Disk or the Halo?
We study the Milky Way region (|Z|< 3.0 kpc) where the thickdisk and inner halo overlap by using the kinematics of local bluehorizontal branch (BHB) stars (within 1 kpc) and new samples of BHBstars and A-type stars from the Century Survey. We derive Galactic U, V,and W velocities for these BHB and A-type star samples using propermotions from the NOMAD catalog. The mean velocities and the velocitydispersions of the BHB samples (|Z| < 3 kpc) are characteristicof the halo, while those of the Century Survey A-type stars arecharacteristic of the thick disk. There is no evidence from our samplesthat the BHB stars rotate with the thick disk in the region |Z| <3 kpc. Nearly a third of the nearby local RR Lyrae stars have diskkinematics and are more metal rich than [Fe/H] ~ –1. Only a fewpercent of the Century Survey BHB (CBHB) stars have these properties.Only one nearby BHB star (HD 130201) is likely to be such a disk starbut selection based on high proper motions will have tended to excludesuch stars from the local sample. The scale height derived from a sampleof local RR Lyrae stars agrees with that of the CBHB stars. The localsamples of BHB stars and metal-weak red giants are too incomplete for asimilar comparison.
| Spectroscopic observations of the first helium nova V445 Puppis
At Asiago Astrophysical Observatory, we observed the peculiar, explosiveobject Nova (V445) Puppis 2000 during its early decline stage betweenJanuary and April 2001. We acquired both high and medium dispersionspectra for the optical wavelengths 3900-7000 Å. The mostremarkable properties of the spectra were an absence of hydrogen linesand unusually strong carbon-ion, emission lines. We identified the mostprominent emission line in the optical region at 6585 Å to be dueto C II 2, 6578 and 6583 Å. The second strongest emission line at5900 Å may be due to Na I D1 and D2, blended by C II 5, 5900 and5902 Å. Prominent emission lines of Fe II, Ti II, Cr II, Si II, MgII, [Fe II], [Ti II], C I, C II, C III, Ca I, He I, and probably of OII, N II, N III, and S II were in addition detected. Some emission linesof Fe II, Ti II, Cr II, Na I, and Mg II were accompanied by P Cygni typeabsorption components blue-shifted by about -500 km s-1. Ourfirst spectrum obtained on January 14, 2001 showed an absorption band ofCN (cyanogen) molecule at 4215 Å. The overall spectral featuresresembled those of classical slow novae, apart from the absence ofhydrogen lines. The appearance of some [Ti II] lines, and a rather highintensity of the emission line of Mg II 23, 6545.8 Å, wereadditional peculiar spectral features of this object. This object may belocated in or beyond the Orion arm, because two sets of interstellarabsorption components of Na I D1 and D2 were detected. Their radialvelocities in the local standard of rest are +16.0 ± 0.4 kms-1 and +73.5 ± 1.0 km s-1. The radialvelocity of this object is estimated to be +224 ± 8 kms-1, which suggests that this object belongs to the old diskpopulation. The distance and the interstellar extinction to the objectare estimated to be 3.5 ? d ? 6.5 kpc and E(B-V) = 0.51 mag,respectively. The derived absolute magnitude at light maximum is -5.8? MV ? -7.1 mag. Our results support the classificationof this object as a helium nova.
| Is a 2004 Leonid meteor spectrum captured in a 182 cm telescope?
Context: It has been thought that fast-moving meteor spectra consist ofonly two excitation temperature regimes: the 5000 K main component andanother hot component at 10 000 K. This belief does not always satisfyobserved spectra due to the lack of sufficient physical correlationamong derived excitation temperatures, observed fluxes, upper energylevels (E_u), and Einstein A coefficients (A_ul) of each spectralemission line. Aims: This work tries to correlate them anddiscovery new excitation temperature regimes in meteor spectra in thevisual to near IR wavelength region. Methods: We focus on theupper energy levels and Einstein A coefficients of observed spectralemission lines. A model fitting the first positive band of nitrogen(N_2) and total number of Si II under quasi-neutral conditions provedthe key to identifying of new components. Results: We haveidentified two new excitation temperature regions in meteor spectra. Oneis a Mid component at 8000 K for N2 and another a Jetcomponent above 10 000 K for Si II. This breakthrough has allowed us toreproduce the meteor spectrum. Conclusions: The spectra ofhigh-speed meteors may consist of more than two excitation temperatureregions including the main, Mid, hot, and Jet components.Appendices are only available in electronic form at http://www.aanda.org
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| The Origins and Evolutionary Status of B Stars Found Far from the Galactic Plane. I. Composition and Spectral Features
The existence of faint blue stars far above the Galactic plane that havespectra that are similar to nearby Population I B stars presents severalinteresting questions. Among them are the following: Can a Population IB star travel from the disk to a position many kiloparsecs above theplane in a relatively short main-sequence lifetime? Is it possible thatsingle massive star formation is occurring far from the Galactic plane?Are these objects something else masquerading as main-sequence B stars?This paper (the first of two) analyzes the abundances of a sample ofthese stars and reveals several that are chemically similar to nearbyPopulation I B stars, whereas others clearly have abundance patternsmore like those expected in blue horizontal-branch (BHB) orpost-asymptotic giant branch stars. Several of those with old evolvedstar abundances also have interesting features of note in their spectra.We also consider why this sample does not have any classical Be starsand identify at least two 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.
| Rotation Velocities of Red and Blue Field Horizontal-Branch Stars
We present measurements of the projected stellar rotation velocities(vsini) of a sample of 45 candidate field horizontal-branch (HB) starsspanning a wide range of effective temperatures, from red HB stars withTeff~=5000K to blue HB stars with Teff of 17,000K.Among the cooler blue HB stars (Teff=7500-11500 K), weconfirm prior studies showing that, although a majority of stars rotateat vsini<15kms-1, there exists a subset of ``fastrotators'' with vsini as high as 30-35 km s-1. All but one ofthe red HB stars in our sample have vsini<10kms-1, and noanalogous rotation bimodality is evident. We also identify anarrow-lined hot star (Teff~=16,000K) with enhancedphotospheric metal abundances and helium depletion, similar to theabundance patterns found among hot BHB stars in globular clusters, andfour other stars that may also belong in this category. We discussdetails of the spectral line fitting procedure that we use to deducevsini and explore how measurements of field HB star rotation may shedlight on the issue of HB star rotation in globular clusters.
| The Century Survey Galactic Halo Project. I. Stellar Spectral Analysis
The Century Survey Galactic Halo Project is a photometric andspectroscopic survey from which we select relatively blue stars(V-R<0.30 mag) as probes of the Milky Way halo. The survey stripspans the range of Galactic latitude 35°
| Catalogue of averaged stellar effective magnetic fields. I. Chemically peculiar A and B type stars
This paper presents the catalogue and the method of determination ofaveraged quadratic effective magnetic fields < B_e > for 596 mainsequence and giant stars. The catalogue is based on measurements of thestellar effective (or mean longitudinal) magnetic field strengths B_e,which were compiled from the existing literature.We analysed the properties of 352 chemically peculiar A and B stars inthe catalogue, including Am, ApSi, He-weak, He-rich, HgMn, ApSrCrEu, andall ApSr type stars. We have found that the number distribution of allchemically peculiar (CP) stars vs. averaged magnetic field strength isdescribed by a decreasing exponential function. Relations of this typehold also for stars of all the analysed subclasses of chemicalpeculiarity. The exponential form of the above distribution function canbreak down below about 100 G, the latter value representingapproximately the resolution of our analysis for A type stars.Table A.1 and its references are only available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/407/631 and Tables 3 to 9are only available in electronic form at http://www.edpsciences.org
| STELIB: A library of stellar spectra at R ~ 2000
We present STELIB, a new spectroscopic stellar library, available athttp://webast.ast.obs-mip.fr/stelib. STELIB consists of an homogeneouslibrary of 249 stellar spectra in the visible range (3200 to 9500Å), with an intermediate spectral resolution (la 3 Å) andsampling (1 Å). This library includes stars of various spectraltypes and luminosity classes, spanning a relatively wide range inmetallicity. The spectral resolution, wavelength and spectral typecoverage of this library represents a substantial improvement overprevious libraries used in population synthesis models. The overallabsolute photometric uncertainty is 3%.Based on observations collected with the Jacobus Kaptein Telescope,(owned and operated jointly by the Particle Physics and AstronomyResearch Council of the UK, The Nederlandse Organisatie voorWetenschappelijk Onderzoek of The Netherlands and the Instituto deAstrofísica de Canarias of Spain and located in the SpanishObservatorio del Roque de Los Muchachos on La Palma which is operated bythe Instituto de AstrofÃsica de Canarias), the 2.3 mtelescope of the Australian National University at Siding Spring,Australia, and the VLT-UT1 Antu Telescope (ESO).Tables \ref{cat1} to \ref{cat6} and \ref{antab1} to A.7 are onlyavailable in electronic form at http://www.edpsciences.org. The StellarLibrary STELIB library is also available at the CDS, via anonymous ftpto cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/402/433
| Distant field blue horizontal branch stars and the mass of the Galaxy - I. Classification of halo A-type stars
This is the first in a series of three papers presenting a newcalculation of the mass of the Galaxy based on radial velocities anddistances measured for a sample of some 100 faint 16 < B < 20field blue horizontal branch (BHB) stars. This study aims to reduce theuncertainty in the measured mass of the Galaxy by increasing the numberof halo objects at Galactocentric distances r > 30 kpc with measuredradial velocities by a factor of 5. Faint A-type stars in the Galactichalo have been identified from ubjr photometry in six UKSchmidt fields. These samples include field BHB stars as well as lessluminous stars of main-sequence surface gravity, which are predominantlyfield blue stragglers. We obtain accurate charge-coupled devicephotometry and spectra to classify these stars. This paper describes ourmethods for separating out clean samples of BHB stars in a way that isefficient in terms of telescope time required. We use the highsignal-to-noise (S/N) ratio spectra of A-type stars of Kinman, Suntzeff& Kraft (published in 1994), and their definitive spectrophotometricΛ classifications, to assess the reliability of two methods, andto quantify the S/N ratio requirements. First we revisit, refine andextend the hydrogen linewidth versus colour relation as a classifier(here called the D0.15-colour method). The second method isnew and compares the shapes of the Balmer lines. With this method (herecalled the scale-width-shape method) there is no need for colours orspectrophotometry. Using the equivalent width of the CaII K line as anadditional filter we find we can reproduce Kinman, Suntzeff &Kraft's Λ classifications with both methods. In a sample of starswith strong Balmer lines, equivalent width Hγ > 13Å[equivalent to the colour range 0 <= (B-V)0<=0.2], halo BHB stars can be separated from halo blue stragglersreliably. For the spectroscopy (i.e. both classification methods) theminimum required continuum S/N ratio is 15 Å-1. For theD0.15-colour method (B-V)0 colours accurate to0.03 mag are needed.
| The determination of Teff for metal-poor A-type stars using V and 2MASS J, H and K magnitudes
Effective temperatures (T_eff) can be determined from (V-J)_0, (V-H)_0and (V-K)_0 colours that are derived from 2MASS magnitudes. This givesanother way to estimate the T_eff of faint blue halo stars (V la 15)whose temperatures are now usually deduced from bo.Transformations (adapted from Carpenter \cite{carp01b}) are used tochange colours derived from the 2MASS data to the Johnson system. T_effis then derived from these colours using an updated Kurucz model. Tablesare given to derive T_eff as a function of (V-J)_0, (V-H)_0 and (V-K)_0for a variety of metallicities and log g suitable for blue horizontalbranch and main sequence stars. The temperatures obtained in this wayare compared with those in the recent literature for various stars with5 <= V <= 15 and T_eff in the range 6500 to 9500 K; systematicdifferences are ~ 100 K. An exception is the sample of BHB starsobserved by Wilhelm et al. (\cite{wbsl99}) whose T_eff are significantlycooler than those we derive by an amount that increases with increasingtemperature. NOAO is operated by the Association of Universities forresearch in Astronomy, Inc., under contract with the National ScienceFoundation. Tables 2 and 3 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http:/ /cdsweb.u-strasbg.fr/cgi-bin/ qcat?J/ A+A/391/1039
| MWC 560: An SS 433 type object with a white dwarf
Spectral variations of the peculiar symbiotic object MWC 560 (V694 Mon)have been monitored for 10 years since 1991. The radial velocity of theblue edge of the broad absorption components of H I lines is measured toevaluate the outflow velocity of the jet. The variation of the outflowvelocity suggests that there are active and stable stages in thissystem. The outflow velocity in the stable stage seems to vary accordingto the long-term light variation with a period of 1930 days. Thisvariation of the outflow velocity could be explained with a model of gasoutflow from an accretion disk precessing with a period of 1930 days. Ifthe observed amplitude of the light variation, Delta mpg =~0.72 mag, was purely due to the precession, the maximum inclination ofthe disk to the line of sight should be about 59 degrees. Since theoutflow is observed always as absorption, the open angle of the outflowshould be larger than 59 degrees. However, the amplitude of the lightvariation due to the precession of the disk seems to be still ratheruncertain. In the active stage the outflow velocity was much higher (inthe negative sense) than in the stable stage, and rapid variations ofthe outflow velocity were observed. During the outburst in 1990, thisobject was in the active stage, while no significant brightening wasobserved in the active stages in 1993 and 1999 at least in the V band.The durations of the active stages were several months.
| The spectrum of the recurrent nova U Scorpii during the 1999 outburst
An optical spectrum covering the range ??4300-6900Å, of the recurrent nova U Sco in outburst was taken on February26th 1999, only 16 hours after maximum. Broad emission lines of H I, HeI, N II, N III were seen on the spectrum, while the emission line of HeII ?4686 was not yet seen. The FWHM of the emission component ofH? was 8000 km s-1, and the FWZI was roughly 12000 kms-1. The emission line of H? had blue (-3250 kms-1), central (+30 km s-1), and red (+2770 kms-1) peaks, among which the red one was the most prominent. Anarrow absorption component of H? blue-shifted by -4850 kms-1, was seen. The other prominent lines had a main emissionpeak red-shifted by 2000- 3000 km s-1, and a weak secondarypeak blue-shifted by -2000- -3000 km s-1. Most of He I and NII lines were flanked by a narrow absorption component blue-shifted byabout -4300 km s-1, which was a good clue for the detailedidentification of these lines. These absorption components and someemission lines of N II faded very rapidly and nearly disappeared one dayafter our observation. The widths of the emission lines decreased withtime. The radial velocities of three emission peaks of H? were-1560 km s-1, +60 km s-1, and +1800 kms-1 on March 14th, 17 days after maximum, when the blue onebecame stronger than the others. The helium abundance by the number ofatom of the ejecta is estimated as N(He)/N(H) = 0.16+/- 0.02 which ismuch lower than those found in previous works, and is not different fromthose of normal classical novae. Adopting the distance 6 kpc, the massof the ejecta is estimated as 3- 9x 10-7 Msun.
| Kurucz Model Energy Distributions: A Comparison With Real Stars. II. Metal-Deficient Stars
Energy distributions of synthetic spectra for Kurucz model atmospheresare compared with observed energy distributions of metal-deficient starsof the blue horizontal-branch (BHB), F--G--K subdwarf (SD) and G--Kgiant (MDG) types. The best coincidence of the synthetic and observedenergy curves is found for BHB stars. The largest differences are foundin the ultraviolet wavelengths for subdwarfs and cool MDGs. Theinfluence of errors of effective temperatures, gravities andmetallicities is estimated.
| Stellar parameters for Pop II A-type stars from IUE spectra and new-ODF ATLAS9 model atmospheres
Stellar parameters for twenty-seven field horizontal branch A-typestars, a post-AGB star (BD +32 2188), and a possible cool sdB star (BD+00 0145) were obtained by fitting the whole IUE energy distributionstaken from the IUE-INES archive to the ultraviolet energy distributionspredicted by new-ODF ATLAS9 model atmospheres, which include theLyman-alpha H-H+ and H-H quasi-molecular absorptions near1400 Å and 1600 Å. The sample of stars was extensivelystudied by Kinman et al. (2000), who derived stellar parameters for themby using visual observations and also an ultraviolet color index. Theeffective temperatures obtained by fitting the IUE spectra to thenew-ODF models agree with T_eff derived by Kinman et al. (2000) for mostof the stars in the sample. The gravities from UV agree with those fromKinman et al. (2000) for stars hotter than about 8700 K, while they arelower, on average, by 0.3 dex for the cooler stars. The same discrepancyis present when log g from the ultraviolet energy distribution iscompared with log g from the visible energy distribution. The differenceis insensitive to reddening, microturbulent velocity, metallicity, ormixing-length parameter for the treatment of the convection. Figures A.1to A.15 are only available in electronic form athttp://www.edpsciences.org
| A spectroscopic study of field BHB star candidates
New spectroscopic observations are presented for a sample of thirty-oneblue horizontal branch (BHB) star candidates that are sufficientlynearby to have reliable proper motions. Comments are given on a furthertwenty-five stars that have previously been suggested as BHB starcandidates but which were not included in our sample. Moderatelyhigh-resolution spectra (lambda /Delta lambda ~ 15 000) of twenty fiveof our program stars were taken with the coudé feed spectrographat Kitt Peak. Twelve of the program stars were also observed with theCAT spectrograph at ESO. Six of these program stars were observed fromboth hemispheres. IUE low-resolution spectra are available for most ofour candidates and were used, in addition to other methods, in thedetermination of their Teff and reddening. A compilation ofthe visual photometry for these stars (including new photometry obtainedat Kitt Peak) is also given. Abundances were obtained from these spectrausing models computed by Castelli with an updated version of the ATLAS9code (Kurucz 1993a). All thirty one candidates are halo stars. Of these,twenty eight are classified as BHB stars because: [(1)]they lie close tothe ZAHB (in a similar position to the BHB stars in globular clusters)in the Teff versus log g plot. For all but one of thesestars, far-UV data were available which were consistent with other data(Strömgren photometry, energy distributions, Hγ profiles) forderiving Teff and log g. [(2)]they have a distribution of kms-1i (<=40 km s-1) that is similar to thatfound for the BHB in globular clusters. Peterson et al. (1995) and Cohen& McCarthy (1997) have shown that the BHB stars in the globularclusters M13 and M92 have a higher km s-1i (<= 40 kms-1) than those in M3 and NGC 288 (<=20 kms-1). The mean deprojected rotational velocity (/line{v}) wascalculated for both the two globular clusters and the nearby BHB starsamples. A comparison of these suggests that both globular cluster kms-1i types are present in our nearby sample. No obvious trendis seen between km s-1i and either (B-V)o or [Fe/H].[(3)]they have -0.99>=[Fe/H]>=-2.95 (mean [Fe/H] -1.67; dispersion0.42 dex), which is similar to that found for field halo RR Lyrae andred HB stars. These local halo field stars appear (on average) to bemore metal-poor than the halo globular clusters. The local sample of redgiant stars given by Chiba & Yoshii (1998) contains a greaterfraction of metal-poor stars than either our halo samples or the haloglobular clusters. The stars in our sample that have a Teffthat exceeds about 8 500 K show the He i (lambda 4471) line with astrength that corresponds to the solar helium abundance. [(4)]they showa similar enhancement of the alpha -elements (< [Mg/Fe]right > =+0.43+/-0.04 and also < [Ti/Fe]right > = +0.44+/-0.02) to thatfound for other halo field stars of similar metallicity. Based onobservations obtained at KPNO, operated by the Association ofUniversities for Research in Astronomy, Inc., under contract with theNational Science Foundation, and the European Southern Observatory,Chile. Tables 4 and 5 are only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr
| X-ray/optical observations of XTE J0421+560/CI Cam in quiescence
We report on a BeppoSAX observation of the transient X-ray sourceXTE J0421+560 during quiescence performed ~ 150 daysafter the 1998 April outburst. The source had an unabsorbed 0.5-10 keVflux of 6.7x 10-12 erg cm-2 s-1 and wasstill remarkably soft with most of the emission below 2 keV. The X-rayspectrum can be fit with the same two-temperature model as the outburstobservations. There is evidence for the presence of an Iron emissionfeature at ~ 7 keV. We report also on a series of optical observationsperformed using the 72 cm Teramo-Normale Telescope (TNT) of the TeramoObservatory, and the 1.5 m Loiano Telescope of the Bologna Observatory.The optical spectrum includes very strong Balmer emission lines, He I,[Fe II], and [O I] features. From the observed L_x/L_opt ~10-3 the quiescent optical emission cannot be due tore-processing of the X-rays, but has to be generated in the opticalcompanion or the circumstellar material. Moreover, the quiescent X-rayluminosity cannot be due to the optical star if it is of spectral typeOB. Although the nature of the compact object present in the XTEJ0421+560/CI Cam system cannot be firmly established, we speculate thatit is most probably a white dwarf.
| Kinematical trends among the field horizontal branch stars
Horizontal branch (HB) stars in the field of the Milky Way can be usedas tracers for the study of early stages of the evolution of our galaxy.Since the age of individual HB stars is not known a priori, we havestudied the kinematics of a sample of field HB stars measured withHipparcos to look for signs of age and population nature. Our samplecomprises 14 HBA, 2 HBB and 5 sdB/O stars. We found that the kinematicsof the HBA stars is very different from that of the sdB/O stars(including those from an earlier study). The HBA stars have low orbitalvelocities, some are even on retrograde orbits. Their orbits have largeeccentricities and in many cases reach large distances above thegalactic plane. In contrast, the sdB/O stars show disk-like orbitalcharacteristics. The few HBB stars (with T_eff> 10,000 K) in oursample seem to have kinematics similar to that of the sdB/O stars. Inorder to see if there is a trend among the HB stars in their kinematics,we investigated also RR Lyrae stars measured with Hipparcos. Here wefound a mixed kinematical behaviour, which was already known fromprevious studies. Some RR Lyrae stars have disk-like orbits (most ofthese being metal rich) but the majority has halo-like orbits, verysimilar to those of our HBA stars. Since the atmospheres of most typesof HB stars do not reflect original metallicities any more thekinematics is the only aspect left to study the origin and populationmembership of these stars. Thus, the clear trend found in kinematics ofstars along the HB, which is also a sequence in stellar mass, shows thatthe different kinds of field HB stars arose from stars having differentorigins in age and, e.g., metallicity or mass loss rate. Based in parton HIPPARCOS data
| Determination of the temperatures of selected ISO flux calibration stars using the Infrared Flux Method
Effective temperatures for 420 stars with spectral types between A0 andK3, and luminosity classes between II and V, selected for a fluxcalibration of the Infrared Space Observatory, ISO, have been determinedusing the Infrared Flux Method (IRFM). The determinations are based onnarrow and wide band photometric data obtained for this purpose, andtake into account previously published narrow-band measures oftemperature. Regression coefficients are given for relations between thedetermined temperatures and the photometric parameters (B2-V1), (b-y)and (B-V), corrected for interstellar extinction through use ofHipparcos parallaxes. A correction for the effect of metallicity on thedetermination of integrated flux is proposed. The importance of aknowledge of metallicity in the representation of derived temperaturesfor Class V, IV and III stars by empirical functions is discussed andformulae given. An estimate is given for the probable error of eachtemperature determination. Based on data from the ESA HipparcosAstrometry Satellite.
| A search for magnetic stars in late stages of stellar evolution
No abstract submitted
| Identification of lambda Bootis stars using IUE spectra. I. Low resolution data
An analysis of the stars included in the catalogue of lambda Bootisstars by Paunzen et al. (1997) and which also have IUE observations ispresented here. Population I A-F type stars as well as field horizontalbranch stars were also included in the analysis. Using line-ratios ofcarbon to heavier elements (Al and Ni) allows us to establishunambiguous membership criteria for the lambda Bootis group. Tables 1-3are only available in electronic form at CDS via anonymous ftp tocdsarc.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
| The Fundamental Parameters of Field Horizontal-Branch Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....112.2291G&db_key=AST
| Spectral Characteristics of Field Horizontal-Branch Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....112.2286C&db_key=AST
| A Preliminary Discussion of the Kinematics of BHB and RR Lyrae Stars Near the North Galactic Pole
The radial velocity dispersion of 67 RR Lyrae and BHB stars that aremore than 4 kpc above the galactic plane at the North Galactic Pole is?110 km s-1 and shows no trend with Z (the heightabove the galactic plane). Nine stars with kpc show a smaller velocitydispersion (40±9 km s-1) as is to be expected ifthey mostly belong to a population with a flatter distribution. BothRR Lyrae stars and BHB stars show evidence of stream motion; the mostsignificant is in fields RR 2 and RR 3, where 24 stars in the range4.0?Z?11.0 kpc have a mean radial velocity of -59±16 kms-1. Three halo stars in field RR 2 appear to be part of amoving group with a common radial velocity of -90 km s-1The streaming phenomenon therefore occurs over a range of spatialscales. The BHB and RR Lyrae stars in our sample both have a similarrange of metallicity (-1.2?[Fe/H]?-2.2). Proper motions of BHBstars in fields SA 57 (NGP) and the anticenter field (RR 7) (both ofwhich lie close to the meridional plane of the Galaxy) show that thestars that have Z<4 kpc as well as those with Z>4 kpc have aGalactic V motion that is <-200 km/s and which is characteristic ofthe halo. Thus the stars that have a flatter distribution are reallyhalo stars and not members of the metal-weak thick disk.
| Classification of Population II Stars in the Vilnius Photometric System. I. Methods
The methods used for classification of Population II stars in theVilnius photometric system are described. An extensive set of standardswith known astrophysical parameters compiled from the literature sourcesis given. These standard stars are classified in the Vilnius photometricsystem using the methods described. The accuracy of classification isevaluated by a comparison of the astrophysical parameters derived fromthe Vilnius photometric system with those estimated from spectroscopicstudies as well as from photometric data in other systems. For dwarfsand subdwarfs, we find a satisfactory agreement between our reddeningsand those estimated in the uvbyscriptstyle beta system. The standarddeviation of [Fe/H] deter mined in the Vilnius system is about 0.2 dex.The absolute magnitude for dwarfs and subdwarfs is estimated with anaccuracy of scriptstyle <=0.5 mag.
| A search for stars with strong magnetic fields among horizontal-branch stars and hot subdwarfs
Observations obtained with the 6-m BTA telescope for a few A, Bhorizontal-branch stars and hot subdwarfs have been used to measuretheir effective magnetic fields. No magnetic fields similar to those ofAp, Bp main-sequence stars were found.
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| A search for stars with strong magnetic fields among horizontal-branch stars and hot subdwarfs
Not Available
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הכנס מאמר חדש
לינקים קשורים
הכנס לינק חדש
משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | כלב קטן |
| התרוממות ימנית: | 07h36m11.77s |
| סירוב: | -00°08'15.6" |
| גודל גלוי: | 9.072 |
| תנועה נכונה: | -25.5 |
| תנועה נכונה: | -83.4 |
| B-T magnitude: | 9.205 |
| V-T magnitude: | 9.083 |
קטלוגים וכינוים:
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