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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).
| Near-Infrared Observations of the Massive Star Forming Region IRAS 23151+5912
Near-infrared images and K-band spectroscopy of the massive star-formingregion IRAS 23151+5912 are presented. The JHK' images reveal anembedded infrared cluster associated with infrared nebula, and theH2 (2.12μm) narrow-band image provides for the first timeevidence of outflow activity associated with the cluster. That thecluster is young can be shown by the high percentage of infrared excesssources and the outflow activity. We suggest an age of the cluster of 106 yr. Eight young stars are found in the brightnebular core around IRAS 23151+5912. By the color-magnitude diagrams ofthe cluster, we found five high-mass YSOs and four intermediate-massYSOs in the cluster. Eight H2 emission features arediscovered in the region with a scattered and non-axisymmetricdistribution, indicating the existence of multiple outflows driven bythe cluster. Diffuse H2 emission detected to the north and tothe west of the cluster may result from UV leakage of the cluster. Brγ, H2, and CIV emission lines are found in the K-bandspectrum of the brightest source, NIRS 19, indicating the presence ofenvelope, stellar wind, and shock in the circumstellar environment. Wehave estimated an O7--O9 spectral type for the central massive YSO (20 30 Mȯ), with an age of less than 1 ×106 yr
| Near-infrared polarimetric and spectrometric study of the massive star-forming region S87
We present JHK' imaging polarimetry for the massive star-forming regionS87, and K-band spectrometry from 2.0 to 2.35 μm for several infraredsources in the region. The polarimetric patterns of S87E reveal a deeplyembedded source (DES-S87) associated with reflection nebulosities.Exciting OH maser and 1.3 mm dust continuum emission, the DES-S87 issuggested to be the youngest star in S87 and the driving source ofbipolar CO outflow in the region. A blue cavity is discovered in the[J-K'] color image, to the southwest of DES. Radial dependence ofpolarization degrees in the cavity could be fitted to the slab model ofoutflows at an inclination of 60° out of the planeof the sky (Minchin et al. \cite{Min91b}b). The nebular complex of S87Ecan be divided into three area. The North nebula, exhibiting a bipolarstructure, may represent a bipolar outflow in the northwest-southeastdirection. The southwest nebula traces the blueshifted CO outflow andcorresponds to the cavity structure discovered in the [J-K'] colorimage. The nebular structure of S87E suggests a quadrupolar outflowdriven by DES-S87. A well-defined centrosymmetric pattern is found inthe nebula of S87W with high degrees of polarization, which indicatessingle scattering off small dust grains in the reflection nebula. Thepolarimetric vectors around NIRS A show a polarization disk featureoriented in the southeast-northwest direction. Strong Brγ emissionand H2 emissions are found in the K-band spectra, indicatingthe presences of strong stellar wind, envelope/disk, shocked gas, andhigh-density PDRs in the circumstellar environment of S87E and S87W.According to the K-band spectrum, the mass of DES-S87E is estimated tobe 20 Mȯ.
| A Method of Correcting Near-Infrared Spectra for Telluric Absorption
We present a method for correcting near-infrared medium-resolutionspectra for telluric absorption. The method makes use of a spectrum ofan A0 V star, observed near in time and close in air mass to the targetobject, and a high-resolution model of Vega, to construct a telluriccorrection spectrum that is free of stellar absorption features. Thetechnique was designed specifically to perform telluric corrections onspectra obtained with SpeX, a 0.8-5.5 μm medium-resolutioncross-dispersed spectrograph at the NASA Infrared Telescope Facility,and uses the fact that for medium resolutions there exist spectralregions uncontaminated by atmospheric absorption lines. However, it isalso applicable (in a somewhat modified form) to spectra obtained withother near-infrared spectrographs. An IDL-based code that carries outthe procedures is available for downloading via the World Wide Web.Based on observations obtained with the Infrared Telescope Facility,which is operated by the University of Hawaii under contract to theNational Aeronautics and Space Administration.
| 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
| CO 1st overtone spectra of cool evolved stars: Diagnostics for hydrodynamic atmosphere models
We present spectra covering the wavelength range 2.28 to 2.36 mu m at aresolution of Delta lambda = 0.0007 mu m (or R = 3500) for a sample of24 cool evolved stars. The sample comprises 8 M supergiants, 5 M giants,3 S stars, 6 carbon stars, and 2 RV Tauri variables. The wavelengthscovered include the main parts of the 12C16O v =2-0 and 3-1 overtone bands, as well as the v = 4-2 and 13CO v= 2-0 bandhead regions. CO lines dominate the spectrum for all the starsobserved, and at this resolution most of the observed features can beidentified with individual CO R- or P-branch lines or blends. Theobserved transitions arise from a wide range of energy levels extendingfrom the ground state to E/k > 20 000 K. We looked for correlationsbetween the intensities of various CO absorption line features and otherstellar properties, including IR colors and mass loss rates. Two usefulCO line features are the v = 2-0 R14 line, and the CO v = 2-0 bandhead.The intensity of the 2-0 bandhead shows a trend with K-[12] color suchthat the reddest stars (K-[12] > 3 mag) exhibit a wide range in 2-0bandhead depth, while the least reddened have the deepest 2-0 bandheads,with a small range of variation from star to star. Gas mass loss ratesfor both the AGB stars and the red supergiants in our sample correlatewith the K-[12] color, consistent with other studies. The data implythat stars with dot M_gas < 5x 10-7 Msuny-1 exhibit a much narrower range in the relative strengthsof CO 2-0 band features than stars with higher mass loss rates. Therange in observed spectral properties implies that there are significantdifferences in atmospheric structure among the stars in this sample.Figures 4-9, 11-14, 16, 17, 19-21, 23, 24 are only avalaible inelectronic form at http://www.edpsciences.org
| 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
| 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 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.
| Research into the close binary QQ Cassiopeae with the primary component of the arly spectral type.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1989CoSka..18....7K&db_key=AST
| 'Normal' main sequence AO stars of low rotational velocity
A set of v sin i values has been derived in a homogeneous way for allthe northern unevolved AO stars which are listed in the Bright StarCatalogue and which are known to rotate more slowly than 40 km/s. Themethod used for the v sin i measurement employs the FFT algorithm and isdesigned to make the best use possible of line profiles obtained fromphotographic spectrograms. It is interesting to notice that, from afirst glance analysis of the spectra obtained, the suspicion arises thatAO single stars with atmospheric solar composition are very rare or evennonexistent among slow rotators (v sin i of less than 15 km/s).
| The local system of early type stars - Spatial extent and kinematics
Published uvby and H-beta photometric data and proper motions arecompiled and analyzed to characterize the structure and kinematics ofthe bright early-type O-A0 stars in the solar vicinity, with a focus onthe Gould belt. The selection and calibration techniques are explained,and the data are presented in extensive tables and graphs and discussedin detail. The Gould belt stars of age less than 20 Myr are shown togive belt inclination 19 deg to the Galactic plane and node-lineorientation in the direction of Galactic rotation, while the symmetricaldistribution about the Galactic plane and kinematic properties (purecircular differential rotation) of the belt stars over 60 Myr oldresemble those of fainter nonbelt stars of all ages. The unresolveddiscrepancy between the expansion observed in the youngest nearby starsand the predictions of simple models of expansion from a point isattributed to the inhomogeneous distribution of interstellar matter.
| 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
| Photoelectric measures of variable stars observed at MT. Kobau (1970-73).
Not Available
| Rotational Velocities of a0 Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974ApJS...28..101D&db_key=AST
| Four-color and Hβ photometry for the brighter AO type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&AS....5..109C&db_key=AST
| The corrected magnitudes and colours of 278 stars near S.A. 1-139 in the UBV system
Not Available
| Computation of Elements of Eclipsing Binary Stars by High-Speed Computing Machines.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1962ApJS....7..351H&db_key=AST
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| קבוצת-כוכבים: | קאסיופיאה |
| התרוממות ימנית: | 23h48m53.90s |
| סירוב: | +59°58'44.0" |
| גודל גלוי: | 6.34 |
| מרחק: | 105.374 פארסק |
| תנועה נכונה: | 49.2 |
| תנועה נכונה: | 14.5 |
| B-T magnitude: | 6.312 |
| V-T magnitude: | 6.322 |
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