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Statistical Constraints for Astrometric Binaries with Nonlinear Motion
Useful constraints on the orbits and mass ratios of astrometric binariesin the Hipparcos catalog are derived from the measured proper motiondifferences of Hipparcos and Tycho-2 (Δμ), accelerations ofproper motions (μ˙), and second derivatives of proper motions(μ̈). It is shown how, in some cases, statistical bounds can beestimated for the masses of the secondary components. Two catalogs ofastrometric binaries are generated, one of binaries with significantproper motion differences and the other of binaries with significantaccelerations of their proper motions. Mathematical relations betweenthe astrometric observables Δμ, μ˙, and μ̈ andthe orbital elements are derived in the appendices. We find a remarkabledifference between the distribution of spectral types of stars withlarge accelerations but small proper motion differences and that ofstars with large proper motion differences but insignificantaccelerations. The spectral type distribution for the former sample ofbinaries is the same as the general distribution of all stars in theHipparcos catalog, whereas the latter sample is clearly dominated bysolar-type stars, with an obvious dearth of blue stars. We point outthat the latter set includes mostly binaries with long periods (longerthan about 6 yr).
| Minimizing Strong Telluric Absorption in Near-Infrared Stellar Spectra
We have obtained high-resolution spectra (R~25,000) of an A star overvarying air mass to determine the effectiveness of telluric removalwithin the limit of a high signal-to-noise ratio. The near-infrared lineHe I at 2.058 μm, which is a sensitive indicator of physicalconditions in massive stars, supergiants, H II regions, and YSOs,resides among pressure-broadened telluric absorption from CO2and water vapor that varies with both time and observed air mass. Ourstudy shows that in the limit of bright stars at high resolution,accuracies of 5% are typical for high-air-mass observations (greaterthan 1.9), improving to a photon-limited accuracy of 2% at smaller airmasses (less than 1.15). We find that by using the continuum betweentelluric absorption lines of a rovibrational fan, a photon-limited 1%accuracy is achievable.
| The status of Galactic field λ Bootis stars in the post-Hipparcos era
The λ Bootis stars are Population I, late B- to early F-typestars, with moderate to extreme (up to a factor 100) surfaceunderabundances of most Fe-peak elements and solar abundances of lighterelements (C, N, O and S). To put constraints on the various existingtheories that try to explain these peculiar stars, we investigate theobservational properties of λ Bootis stars compared with areference sample of normal stars. Using various photometric systems andHipparcos data, we analyse the validity of standard photometriccalibrations, elemental abundances, and Galactic space motions. Therecrystallizes a clear picture of a homogeneous group of Population Iobjects found at all stages of their main-sequence evolution, with apeak at about 1 Gyr. No correlation of astrophysical parameters such asthe projected rotational velocities or elemental abundances with age isfound, suggesting that the a priori unknown mechanism, which createsλ Bootis stars, works continuously for late B- to early F-typestars in all stages of main-sequence evolution. Surprisingly, the sodiumabundances seem to indicate an interaction between the stars and theirlocal environment.
| 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
| uvby photometry of the CP stars HR 149, HD 32966, HD 171782, and HR 7911
Differential Strömgren uvby observations from the Four CollegeAutomated Photoelectric Telescope (FCAPT) are presented for the CP starsHR 149 and HR 7911 and the mCP stars HD 32966 and HD 171782. TheMercury-Manganese star HR 149 is found to be constant while HR 7911 witha period of 5.9617 days probably has a component which is a magnetic CPstar. Improved periods were derived for HD 32966 and HD 171782 of 3.0927and 4.4674 days, respectively. The former is a rather large amplitudemCP star. Both have at least one light curve different in shape from theothers observed. Tables 2, 3, 4 and 5 are only available in electronicform at the CDS 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/390/1023
| A Spectroscopic Study of the Envelope of the Recurrent Nova CI Aquilae
Not Available
| 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
| Infrared spectroscopic variability of Cygnus X-3 in outburst and quiescence
We present four epochs of high-resolution infrared spectroscopy of thepeculiar X-ray binary Cygnus X-3. The observations cover quiescent,small-flaring and outburst states of the system as defined by radio andX-ray monitoring. The underlying infrared spectrum of the source, asobserved during radio and X-ray quiescence and small-flaring states, isone of broad, weak Heii and Nv emission. Spectral variability in thisstate is dominated by modulation at the 4.8-h orbital period of thesystem. H-band spectra confirm the significant hydrogen depletion of themass donor. The closest spectral match to the quiescent infraredspectrum of Cyg X-3 is an early-type WN Wolf-Rayet star. In outburst,the infrared spectrum is dramatically different, with the appearance ofvery strong twin-peaked Hei emission displaying both day-to-dayvariability and V(iolet)/R(ed) variations with orbital phase. We arguethat the twin-peaked emission cannot arise in relativistic jets or,unless the distance to Cyg X-3 is severely overestimated, an accretiondisc. The most likely explanation appears to be an enhanced stellar windfrom the companion. Thus X-ray and radio outbursts in this system arelikely to originate in mass-transfer, and not disc, instabilities, andthe lengthening of the orbital period will not be smooth but will beaccelerated during these outbursts. Furthermore, the appearance of theselines is suggestive of an asymmetric emitting region. We propose thatthe wind in Cyg X-3 is significantly flattened in the plane of thebinary orbit. This may explain the observed twin-peaked Hei features aswell as reconciling a massive Wolf-Rayet secondary with the relativelysmall optical depth to X-rays, if the disc wind is inclined at someangle to the line of sight. A small set of observations followingoutburst, when the system was returning to a more quiescent X-ray andradio state, reveal strong Hei 2.058-μm absorption with a clear PCygni profile, at the same time as the more common weak Heii and Nvfeatures. In a disc-wind geometry this can be interpreted as absorptionin the densest, accelerating regions of the wind which can be vieweddirectly if the disc is inclined at some angle to the line of sight.
| Absolute declinations with the photoelectric astrolabe at Calern Observatory (OCA)
A regular observational programme with a photoelectric astrolabe havebeen performed at ``Observatoire du Calern" (Observatoire de laCôte d'Azur, OCA, phi = +43() o44′55.011″; lambda =-0() h27() m42.44() s, Calern, Caussols, France) for the last twentyyears. It has been almost fully automatized between 1984 and 1987. Since1988 the photoelectric astrolabe was used without any modification. Inaddition to determining the daily orientation of the local vertical, theyearly analysis of the residuals permits to derive corrections to theused star catalogue \cite[(Vigouroux et al. 1992)]{vig92}. A globalreduction method was applied for the ASPHO observations. The new form ofthe equations \cite[(Martin & Leister 1997)]{mar97} give us thepossibility of using the entire set of the observing program using datataken at two zenith distances (30() o and 45() o). The program containsabout 41648 stars' transits of 269 different stars taken at``Observatoire du Calern" (OCA). The reduction was based on theHIPPARCOS system. We discuss the possibility of computing absolutedeclinations through stars belonging simultaneously to the 30() o and45() o zenith distances programmes. The absolute declination correctionswere determined for 185 stars with precision of 0.027arcsec and thevalue of the determined equator correction is -0.018arcsec +/-0.005arcsec . The instrumental effects were also determined. The meanepoch is 1995.29. Catalogue only available at CDS in electronic from viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Mapping the contours of the Local bubble: preliminary results
We present preliminary results from a long-term program of mapping theneutral absorption characteristics of the local interstellar medium,taking advantage of Hipparcos stellar distances. Equivalent widths ofthe NaI D-line doublet at 5890 Å are presented for thelines-of-sight towards some 143 new target stars lying within 300 pc ofthe Sun. Using these data which were obtained at the Observatoire deHaute Provence, together with previously published NaI absorptionmeasurements towards a further 313 nearby targets, we present absorptionmaps of the distribution of neutral gas in the local interstellar mediumas viewed from 3 different galactic projections. In particular, thesemaps reveal the Local Bubble region as a low neutral densityinterstellar cavity in the galactic plane with radii between 65-250 pcthat is surrounded by a (dense) neutral gas boundary (or ``wall''). Wehave compared our iso-column contours with the contours derived bySnowden et al. (\cite{snowden98}) using ROSAT soft X-ray emission data.Consistency in the global dimensions derived for both sets of contoursis found for the case of a million degree hot LB plasma of emissivity0.0023 cm(-6) pc with an electron density of 0.005 cm(-2) . We havedetected only one relatively dense accumulation of cold, neutral gaswithin 60 pc of the Sun that surrounds the star delta Cyg, and note thatthe nearest molecular cloud complex of MBM 12 probably resides at thevery edge of the Local Bubble at a distance of ~ 90 pc. Our observationsmay also explain the very different physical properties of the columnsof interstellar gas in the line-of-sight to the two hot stars epsilonCMa and beta CMa as being due to their locations with respect to theBubble contours. Finally, in the meridian plane the LB cavity is foundto be elongated perpendicularly to the Gould's Belt plane, possiblybeing ``squeezed'' by the expanding shells of the Sco-Cen andPerseus-Taurus OB associations. Tables 1 and 2 are also available inelectronic form at the CDS (Strasbourg) via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The ROSAT all-sky survey catalogue of optically bright main-sequence stars and subgiant stars
We present X-ray data for all main-sequence and subgiant stars ofspectral types A, F, G, and K and luminosity classes IV and V listed inthe Bright Star Catalogue that have been detected as X-ray sources inthe ROSAT all-sky survey; several stars without luminosity class arealso included. The catalogue contains 980 entries yielding an averagedetection rate of 32 percent. In addition to count rates, sourcedetection parameters, hardness ratios, and X-ray fluxes we also listX-ray luminosities derived from Hipparcos parallaxes. The catalogue isalso available in electronic form via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| New Photometric Data for HD 142703 and HD 192640
Not Available
| The Stromvil System: an Effective Combination of Two Medium-Band Photometric Systems
It is shown that the addition to the Stromgren four-color photometricsystem of three passbands at 374, 516 and 656 nm from the Vilniusphotometric system makes the combined system more universal. This newsystem, called the Stromvil system, makes it possible to classify starsof all spectral types, even in the presence of interstellar reddening.This property of the system is especially important in CCD photometry,allowing the photometric classification of very faint stars. Apreliminary calibration of the system in terms of spectral andluminosity classes, temperatures and surface gravities is available. Alist of preliminary standards for the Stromvil system in the regions ofCygnus, Aquila and near the North Celestial Pole is given.
| 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.
| Evaluation of a 512X512-Element Platinum Silicide Schottky-Barrier Infrared Image Sensor and Pilot Observations of Cygnus X Region
We present evaluation of the performance of Mitsubishi's 512X512 elementplatinum silicide (PtSi) Schottky-Barrier infrared image sensor forapplication to astronomical observation. An infrared camera system,incorporating the PtSi array, was built and its performance wasevaluated both in the laboratory and in observations. Dark current, DCstability, noise, quantum efficiency (QE), linearity, and uniformitywere measured. Results of a series of measurements show that the arrayhas potential capability for astronomical use. Several problems such aslow QE and "splashes" are discussed. To demonstrate the effectiveness ofthe array by using this infrared camera, we have mapped an area of 8X9square degrees of the Cygnus X region with a small telescope consistingof a silicon singlet lens. More than 1000 stars brighter than 6.5 mag inH-band were detected in the region. (SECTION: AstronomicalInstrumentation)
| Photometric Examination of CP2-Peculiarity for HD200405, HR44, HR7752 and HR9092
Not Available
| 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.
| Early-type stars in the stellar associations Per OB1, SCO OB1, and CYG OB1 by observations with space telescope 'Glazar'
This paper presents results of observations at 1640 A carried out inSeptember 1988 with the Soviet space telescope Glazar on the regions ofstellar associations Per OB1, Sco OB1, and Cyg OB1. Thirty twophotographs were obtained, on which 94 images of stars were identifiedand measured. In stellar associations Per OB1, Sco OB1, and Cyg OB1, 42,22, and 30 hot stars brighter than 10 mag at 1640 A were detected,respectively. A comparison of Glazar measurements of stellar magnitudeswith those available from TD-1 telescope measurements and from ANSmeasurements showed reasonably good agreement.
| The Distribution of Early Type Stars in the Direction of Stellar Associations PERSEUS-OB1 SCORPIUS-OB1 and CYGNUS-OB1
Not Available
| The R-I color indiuces measured with the S-20 photocathode
Not Available
| Third preliminary catalogue of stars observed with the photoelectric astrolabe of the Beijing Astronomical Observatory.
Not Available
| Spectrophotometry of stars in Cygnus
Preliminary results of the observations of 70 stars of early spectraltypes in Cygnus are presented. Spectrophotometric data have beenobtained which can be used to study the structure of the Galaxy withrelatively high reliability.
| The early A type stars - Refined MK classification, confrontation with Stroemgren photometry, and the effects of rotation
The MK classification system for the early A-type stars is refined, anda parallel system of standards for the broad-lined stars is introduced.With this improved system, stars may be classified with significantlygreater precision than before. It is shown that spectral types in thissystem are not systematically affected by rotational line broadening. Atotal of 372 early A-type stars are classified, and a confrontation ofthese spectral types with Stroemgren photometry reveals a number ofsystematic photometric effects of rotation. In particular, high v sin istars are systematically redder than low v sin i stars of the samespectral type, and the beta index is weakened by rotation. It isconcluded that precise spectral classification in conjunction withStroemgren and H-beta photometry can potentially provide a valuablecheck and input to the theory of the atmospheres of rotating stars.
| New magnitudes and color indices of the Cygnus standard region stars in the Vilnius photometric system.
Not Available
| Catalogue of the energy distribution data in spectra of stars in the uniform spectrophotometric system.
Not Available
| 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.
| Apparent radii and other parameters for 416 B5 V-F5 V stars of the catalogue of the Geneva Observatory
Apparent radius, visual brightness, effective temperature and absoluteradius for 416 B5 v-F5 v stars of the catalogue of the GenevaObservatory (Rufener, 1976) have been determined. Twenty-eight stars,anomalous in log a" versus (m~)o diagrams, have been singled out. A goodcorrelation for seven stars, in common with the list of Hanbury Brown etal. (1974), has been found. Similar parameters determined for 279 B5v-F5 v stars of two preceding papers (Fracassini et al., 1973, 1975)have allowed us to determine the averaged diagrams , and versus (B -V)0 for 695 B5 v-F5 v stars. Moreover, in the present paper a goodcorrelation versus and carefulrelation = -7.40 + 3.31 for B5v-F5 V stars have been determined. Plain correlations between log R/R0and blanketing parameter m2 for some spectral types seem to point outthat there are real differences in the absolute radii of stars of thesame spectral type, in agreement with recent researches on the HRdiagram (Houck and Fesen, 1978). Systematic differences between double(spectroscopic and visual) and single stars are found. In particular,the averaged relation versus shows that A2v-F5 v double stars may have a higher metallicity index m2 and smallerabsolute radii than single stars. Finally, the diagram log v sin iversus log R/R0 confirms some properties of binary systems found byother researchers (Huang, 1966; Plavec, 1970; Levato, 1974; Kitamura andKondo, 1978)
| Narrow-band photometry of Beta Lyrae in 1971
Observations of Beta Lyrae (with HR 6997 as the principal companionstar) are presented, principally of certain strong lines and neighboringcontinuum regions obtained through interference filters of bandwidthsranging from 27.0 to 33.7 A. Light curves in the 3 blue and 3 red bandsare shown, and color indices and emission intensity indices aretabulated. Moreover, a photometric index of emission line strength,analogous to the spectroscopic index of Batten and Sahade (1973), isderived. It is suggested that the H alpha emission comes from a largerregion around the binary star than does the helium emission and isasymmetrical, being weakest near quadrature when the primary star isapproaching earth. The helium emission, by contrast, is moresymmetrical, and varies with binary phase by a larger fractional amount.
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| קבוצת-כוכבים: | ברבור |
| התרוממות ימנית: | 20h27m34.30s |
| סירוב: | +38°26'25.0" |
| גודל גלוי: | 5.62 |
| מרחק: | 82.85 פארסק |
| תנועה נכונה: | -23.6 |
| תנועה נכונה: | -73.1 |
| B-T magnitude: | 5.717 |
| V-T magnitude: | 5.64 |
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