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Speckle Interferometry at the Blanco and SOAR Telescopes in 2008 and 2009
The results of speckle interferometric measurements of binary andmultiple stars conducted in 2008 and 2009 at the Blanco and SOAR 4 mtelescopes in Chile are presented. A total of 1898 measurements of 1189resolved pairs or sub-systems and 394 observations of 285 un-resolvedtargets are listed. We resolved for the first time 48 new pairs, 21 ofwhich are new sub-systems in close visual multiple stars. Typicalinternal measurement precision is 0.3 mas in both coordinates, typicalcompanion detection capability is ?m ~ 4.2 at 0farcs15 separation.These data were obtained with a new electron-multiplication CCD camera;data processing is described in detail, including estimation ofmagnitude difference, observational errors, detection limits, andanalysis of artifacts. We comment on some newly discovered pairs andobjects of special interest.
| Albus 1: A Very Bright White Dwarf Candidate
We have serendipitously discovered a previously unknown, bright source(BT=11.75+/-0.07 mag) with a very blueVT-Ks color, which we have named Albus 1. Aphotometric and astrometric study using Virtual Observatory tools hasshown that it possesses an appreciable proper motion and magnitudes andcolors very similar to those of the well-known white dwarf G191-B2B. Weconsider Albus 1 as a DA-type white dwarf located at about 40 pc. If itsnature is confirmed, Albus 1 would be the sixth brightest isolated whitedwarf in the sky, which would make it an excellent spectrophotometricstandard.
| VSOP: the variable star one-shot project. I. Project presentation and first data release
Context: About 500 new variable stars enter the General Catalogue ofVariable Stars (GCVS) every year. Most of them however lackspectroscopic observations, which remains critical for a correctassignement of the variability type and for the understanding of theobject. Aims: The Variable Star One-shot Project (VSOP) is aimed at (1)providing the variability type and spectral type of all unstudiedvariable stars, (2) process, publish, and make the data available asautomatically as possible, and (3) generate serendipitous discoveries.This first paper describes the project itself, the acquisition of thedata, the dataflow, the spectroscopic analysis and the on-lineavailability of the fully calibrated and reduced data. We also presentthe results on the 221 stars observed during the first semester of theproject. Methods: We used the high-resolution echelle spectrographsHARPS and FEROS in the ESO La Silla Observatory (Chile) to survey knownvariable stars. Once reduced by the dedicated pipelines, the radialvelocities are determined from cross correlation with synthetic templatespectra, and the spectral types are determined by an automatic minimumdistance matching to synthetic spectra, with traditional manual spectraltyping cross-checks. The variability types are determined by manuallyevaluating the available light curves and the spectroscopy. In thefuture, a new automatic classifier, currently being developed by membersof the VSOP team, based on these spectroscopic data and on thephotometric classifier developed for the COROT and Gaia space missions,will be used. Results: We confirm or revise spectral types of 221variable stars from the GCVS. We identify 26 previously unknown multiplesystems, among them several visual binaries with spectroscopic binaryindividual components. We present new individual results for themultiple systems V349 Vel and BCGru, for the composite spectrum star V4385Sgr, for the T Tauri star V1045 Sco, andfor DM Boo which we re-classify as a BY Draconisvariable. The complete data release can be accessed via the VSOP website.Based on data obtained at the La Silla Observatory, European SouthernObservatory, under program ID 077.D-0085.
| Composition of the Interstellar Medium
We present an analysis of the FeII, GeII, MgI, MgII, SI, SII, SiII andZnII interstellar lines for 63 stars. Column density of MgII, SII, SiIIand ZnII is well correlated with distance. However, the column density-- distance relation should be used with care for the estimation of thedistance to OB stars. For stars with large f(H_2) this relation can leadto a large overestimation of the distance. The column densities of MgII,SiII and GeII (our largest samples of data) normalized to their totalhydrogen column densities decrease with interstellar reddening E(B-V) asexpected for elements that are incorporated into dust grains. The GeIIabundance (GeII/H) is lower in dense molecular clouds. The abundances ofall analyzed elements are generally lower than their Solar Systemvalues.
| Search for associations containing young stars (SACY). I. Sample and searching method
We report results from a high-resolution optical spectroscopic surveyaimed to search for nearby young associations and young stars amongoptical counterparts of ROSAT All-Sky Survey X-ray sources in theSouthern Hemisphere. We selected 1953 late-type (B-V~≥~0.6),potentially young, optical counterparts out of a total of 9574 1RXSsources for follow-up observations. At least one high-resolutionspectrum was obtained for each of 1511 targets. This paper is the firstin a series presenting the results of the SACY survey. Here we describeour sample and our observations. We describe a convergence method in the(UVW) velocity space to find associations. As an example, we discuss thevalidity of this method in the framework of the β Pic Association.
| Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample
We are obtaining spectra, spectral types, and basic physical parametersfor the nearly 3600 dwarf and giant stars earlier than M0 in theHipparcos catalog within 40 pc of the Sun. Here we report on resultsfor 1676 stars in the southern hemisphere observed at Cerro TololoInter-American Observatory and Steward Observatory. These resultsinclude new, precise, homogeneous spectral types, basic physicalparameters (including the effective temperature, surface gravity, andmetallicity [M/H]), and measures of the chromospheric activity of ourprogram stars. We include notes on astrophysically interesting stars inthis sample, the metallicity distribution of the solar neighborhood, anda table of solar analogs. We also demonstrate that the bimodal nature ofthe distribution of the chromospheric activity parameterlogR'HK depends strongly on the metallicity, andwe explore the nature of the ``low-metallicity'' chromosphericallyactive K-type dwarfs.
| Deuterium Abundance toward WD 1634-573: Results from the FUSE Mission
We use Far Ultraviolet Spectroscopic Explorer (FUSE) observations tostudy interstellar absorption along the line of sight to the white dwarfWD 1634-573 (d=37.1+/-2.6 pc). Combining our measurement of D I with ameasurement of H I from Extreme Ultraviolet Explorer data, we find a D/Hratio toward WD 1634-573 of D/H=(1.6+/-0.5)×10-5. Incontrast, multiplying our measurements of DI/OI=0.035+/-0.006 andDI/NI=0.27+/-0.05 with published mean Galactic interstellar medium (ISM)gas-phase O/H and N/H ratios yieldsD/HO=(1.2+/-0.2)×10-5 andD/HN=(2.0+/-0.4)×10-5, respectively. Notethat all uncertainties quoted above are 2 ?. The inconsistencybetween D/HO and D/HN suggests that either the OI/H I or the N I/H I ratio toward WD 1634-573 must be different from thepreviously measured average ISM O/H and N/H values. The computation ofD/HN from D I/N I is more suspect, since the relative N and Hionization states could conceivably vary within the local ISM, while theO and H ionization states will be more tightly coupled by chargeexchange. Based on observations made with the NASA-CNES-CSA FarUltraviolet Spectroscopic Explorer (FUSE), which is operated for NASA byJohns Hopkins University under NASA contract NAS 5-32985.
| Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
| HD 30187 B and HD 39927 B: two suspected nearby hot subdwarfs in resolved binaries
In doing a B_T, V_T photometric solution for close Hipparcos doublestars, based on the observations with the Tycho instrument of theHipparcos satellite, we discovered two very blue subluminous componentsof HD 30187 and HD 39927. The position of the components on anobservational HR diagram implies their being sdO or sdB hot subdwarfs.The only previously known sdO component of a visual binary, HD 113001 B,is also confirmed by our photometric data. The two new candidate hotsubdwarfs have parallaxes 8.25 and 10.17 mas, respectively, and withangular separations of about 0.35 arcsec, the orbital periods must be ofthe order of 100 years. This should make it possible to determine theirmasses from observation. Based on observations made with the ESAHipparcos satellite.
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| Temperature determination of the cool DO white dwarf HD 149499B from EUVE observations.
We present a LTE model atmosphere analysis of the EUVE medium and longwavelength spectrum of the cool DO white dwarf HD149499B. Thisobservation in the spectral range 230-700Å supplements a previousanalysis of an ORFEUS spectrum between 912 and 1170Å which yieldedthe atmospheric parameters T_eff_=49500+/-500K and logg=7.97+/-0.08 anda hydrogen-to-helium number ratio of 0.22+/-0.11. The EUVE data are infull agreement with the ORFEUS result and allow a more precisedetermination of the effective temperature (T_eff_=49500+/-200K) and theinterstellar hydrogen column density (N_H_=7x10^18^cm^-2^). None of thefeatures in the EUVE spectrum could be identified with any additionalabsorber besides helium. Exploratory calculations with fully metalblanketed LTE model atmospheres show that the metal abundances predictedby current diffusion theory are clearly at variance with the observedspectrum.
| ORFEUS observations of the DO white dwarf HD 149499B.
We present an analysis of a hig-resolution FUV spectrum(912...1170Angstroems) of the cool DO white dwarf HD 149499 B.Observations were performed with the Berkeley EUV/FUV spectrometer ofthe ORFEUS experiment. The analysis, performed with a grid of LTE modelatmospheres, yielded the basic parameters Teff = 49500+/-500K and log g= 7.97+/-0.08. The photospheric hydrogen Lyman lines in the FUV spectrumindicate the presence of hydrogen: log nH/nHe =-0.65+/-0.12.Theimplications of this finding for the spectral evolution of white dwarfsare discussed. A check of the LTE assumption was performed by acomparison with NLTE atmospheres calculated for appropriate parameters.The interstellar components of the hydrogen Lyman lines are used for anestimate of the hydrogen column towards the HD 149499 system: N_H_ about1x10^19^/cm2.
| The general catalogue of trigonometric [stellar] paralaxes
Not Available
| A large, complete, volume-limited sample of G-type dwarfs. I. Completion of Stroemgren UVBY photometry
Four-colour photometry of potential dwarf stars of types G0 to K2,selected from the Michigan Spectral Catalogues (Vol. 1-3), has beencarried out. The results are presented in a catalogue containing 4247uvby observations of 3900 stars, all south of δ = -26deg. Theoverall internal rms errors of one observation (transformed to thestandard system) of a program star in the interval 8.5 < V < 10.5are 0.0044, 0.0021, 0.0039, and 0.0059, respectively, in V, b-y, m_1_ ,and c_1_. The purpose of the catalogue, combined with earliercatalogues, is to allow selection of a large, complete, volume-limitedsample of G- and K-type dwarfs, investigate their metallicitydistribution, and compare it to predictions of various models ofgalactic chemical evolution. Future papers in this series will discussthese subjects.
| IUE and stars with composite spectra
The IUE contribution to the study of binary stars is reviewed. The valueof ultraviolet spectra in defining the parameters of hot companions indouble systems is emphasized, as this is important for understanding ofthe masses, luminosities, and evolutionary states of both the componentstars. Cataclysmic variables; precataclysmics; symbiotic stars;atmospheric eclipsing binaries; Algols; cool and hot binaries; heavymetal stars; noninteractors; and Cepheids are discussed.
| White dwarf stars at ultraviolet wavelengths
Numerous discoveries with the IUE Observatory have stimulated researchon most spectroscopic types of degenerate dwarf stars. The hottesthelium-rich cases apparently have substantial abundances of certain ionsheavier than helium, due most likely to selective radiativeacceleration. Hydrogen DA stars show trace abundances at temperatures aslow as 20,000 K and provide evidence for modest outflowing winds. CoolerDA stars exhibit mysterious broad features near 1400A and 1600A. Theelement carbon is almost omnipresent in cool helium-rich stars, unlessmetallic features are seen instead. The carbon is most likely dredged-upby a deep convective envelope. The metals are attributed to interstellaraccretion. IUE has played an important role in temperaturedeterminations for helium-rich and magnetic stars. White dwarfcomponents in detached and cataclysmic binaries have been studiedextensively with IUE, often for the first time. Among the potentialresults are mass determinations and information on the photospherictemperature distributions for accreting primaries.
| Mass loss, levitation, accretion, and the sharp-lined features in hot white dwarfs
A study has been conducted of eight white dwarfs, including seven DA andone He-rich types. The study is based on high-resolution observationsconducted with the aid of the International Ultraviolet Explorer. Fourof the dwarfs show features related to heavy elements which are notinterstellar in origin. It is tentatively suggested that, at least inthe hottest low-gravity DA white dwarfs, the observed narrow-linedfeatures are formed in expanding halos or winds associated with thewhite dwarfs. Theoretically, stable white dwarf halos should actually becoronae with temperatures in excess of 1,000,000 K. However, theobserved narrow-lined features do not suggest such high temperatures.The observed radial velocities suggest weak stellar winds in two hotwhite dwarfs, namely, G191-B2B and 2111+49. It is tentatively proposedthat radiative levitation can explain the appearance of the observedmetallic lines in the hot DA white dwarfs.
| Discovery of highly ionized species in the ultraviolet spectrum of Feige 24
A high-resolution ultraviolet spectrum of the nearby (90 pc) white dwarfbinary Feige 24 (DA + M1-2 V) obtained with the InternationalUltraviolet Explorer satellite (IUE) reveals two sets of absorptionfeatures in the species C IV, Si IV, and N V. The low-velocity component(V approximately 1 km/s) arises from the local interstellar gasapparently ionized by the white dwarf. The second component, at highvelocities (V approximately +83 km/s), arises in the atmosphere of thewhite dwarf in the Feige 24 system. The presence of this large velocityshift supplies the first strong evidence for narrow absorption cores dueto high-temperature species in a white dwarf atmosphere. Observationsaround the orbital period will provide a direct measurement of thegravitational redshift and the mass of the white dwarf. The inferredhydrogen density is 0.008 per cu cm toward this source.
| Lanning 14, a new DO white dwarf - Spectrophotometry and atmospheric parameters
Optical spectrophotometric observations are presented and analyzed forLanning 14, which was recently classified as a DO white dwarf and hasone of the strongest He II 4868 absorption lines of any known star, withstrong He Bracket lines and weak He I. An effective temperature of55,000 plus or minus 2500 K, log g near 8, and He/H ratio equal to orgreater than 100, have been derived by means of a new grid of hot,high-gravity, mixed-composition models. It is concluded that Lanning 14is both hotter and more helium-rich than the prototype DO star HZ 21.
| Atmospheres for hot, high-gravity stars. II - Pure helium models
An extensive grid of pure helium stellar model atmosphere calculationsfor hot, high-gravity stars is presented in order to elucidate thenature and characteristics of the progenitors of the DB white dwarfs.Surface gravities range from log g equals 6.0 (1.0) 9.0, and theeffective temperatures from 25,000 K at log g equals 6.0 and 8.0 up totemperatures close to the Eddington limit at each gravity. All modelsassume (1) hydrostatic equilibrium, (2) steady-state statisticalequilibrium, (3) pure helium composition, and (4) plane-parallelgeometry. In addition, most are unblanketed and in LTE, and includeconvective heat transport. It is shown that neutral helium lines arestronger than the unblanketed values by about 15 percent, while thesingly-ionized helium lines are found to be strengthened by about 25percent over a large range of surface gravities and effectivetemperatures. Multichannel colors and detailed He 1 profiles aretabulated for all LTE unblanketed models.
| On the kinematics and ages of wide binaries containing a white dwarf
Radial velocities are reported for the bright nondegenerate members of12 common proper-motion binaries containing a white dwarf. Combiningthese with data already published, the kinematics of 24 systems can bestudied. This sample appears to be a mixture of high- and low-velocityobjects relative to the sun, and some have UVW motions that make themappear to be kinematically young, although some of these pairs can beeliminated after consideration of their cooling times. The additionalspectroscopic clues of emission lines and peculiar spectral typessuggest youth and strengthen the conclusion that the white dwarfcomponents of some of these low-velocity pairs evolved from parent starsthat belong to a young stellar population.
| 80,000 stars an hour
The Automated Plate Scanner (mated to a minicomputer and amicroprocessor controller) can scan two 14 sq in. Palomar Sky Surveyplates simultaneously in about 2.5 h, reading the positions of 100,000stars on each photographic plate with a positional accuracy of about 1micron. Light from a helium-neon laser passes through a 2,250 rpmrotating eight-sided prism to the plates and is focused on aphotomultiplier tube, then processed by means of a threshold detector.With an interactive data-reduction system (including an image-processor)uses of the Scanner, other than proper-motion measurement, includeprocessing both circular and comatic star images, one-dimensional andechelle spectrograms, and extended objects; subtracting backgroundlight, and comparing optical plates with VLA radio 'plates'. Otherpossible applications include photographic photometry of stars inclusters and galaxies and surveys for emission-line objects.
| HD 149499 B - The hottest white dwarf
IUE spectra of the white dwarf component of HD 149499, discovered fromthe Skylab experiments S-019 UV survey, show prominent lines of He II.The star appears to be helium-rich with He/H not less than 1. Theultraviolet fluxes show the temperature to be within the range70,000-100,000 K, with the most probable value near 85,000 K.
| The hot white dwarf HD 149499B
Spectroscopic observations over the wavelength range from 3700 to 5500 Aand UBV photometry of the proposed hot white dwarf HD 149499B arereported. The spectrum is found to be nearly continuous and to lackhydrogen Balmer lines. An absolute visual magnitude of 9.5 isdetermined, along with a heliocentric radial velocity of about 31 km/sand space velocities of (U, V, W) = (-21, +30, -12) km/s. The resultsare taken to confirm the identification of HD 149499B as a hot whitedwarf. It is concluded that: (1) if this star is in the same temperaturerange as other known hot hydrogen-rich degenerates (viz., HZ 43 and F24), the absence of Balmer lines implies that the star ishydrogen-deficient, and (2) if the 4686-A line of He II is present, HD149499B is likely to be a helium-rich DO star like HZ 21.
| Measures of southern visual double stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977PASP...89..588H&db_key=AST
| SKYLAB ultraviolet stellar spectra - A new white dwarf, HD 149499 B
The letter reports the discovery of a cool star with excess brightnessin the vacuum ultraviolet on an objective-prism photograph obtainedduring the second Skylab mission. This star, HD 149499, is of type K0 Vand has a companion with an apparent magnitude of about 11.8; therelatively flat UV spectrum observed at the position of HD 149499 ischaracteristic of a 10th or 11th magnitude unreddened O- or early B-typestar. It is shown that the excess VUV brightness is due to thecompanion, HD 149499B, which probably lies in the region of the H-Rdiagram occupied by the hot white dwarfs. Inspection of white dwarflists indicates that this star is the sixth or seventh brightest whitedwarf known. A maximum orbital motion of 0.025 arcsec/yr is estimatedalong with a period of just under 500 yr.
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| Takýmyýldýz: | Sunak |
| Sað Açýklýk: | 16h38m31.09s |
| Yükselim: | -57°28'11.3" |
| Görünürdeki Parlaklýk: | 8.706 |
| Uzaklýk: | 37.12 parsek |
| özdevim Sað Açýklýk: | 95.1 |
| özdevim Yükselim: | 3.7 |
| B-T magnitude: | 9.69 |
| V-T magnitude: | 8.788 |
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