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CHARM2: An updated Catalog of High Angular Resolution Measurements
We present an update of the Catalog of High Angular ResolutionMeasurements (CHARM, Richichi & Percheron \cite{CHARM}, A&A,386, 492), which includes results available until July 2004. CHARM2 is acompilation of direct measurements by high angular resolution methods,as well as indirect estimates of stellar diameters. Its main goal is toprovide a reference list of sources which can be used for calibrationand verification observations with long-baseline optical and near-IRinterferometers. Single and binary stars are included, as are complexobjects from circumstellar shells to extragalactic sources. The presentupdate provides an increase of almost a factor of two over the previousedition. Additionally, it includes several corrections and improvements,as well as a cross-check with the valuable public release observationsof the ESO Very Large Telescope Interferometer (VLTI). A total of 8231entries for 3238 unique sources are now present in CHARM2. Thisrepresents an increase of a factor of 3.4 and 2.0, respectively, overthe contents of the previous version of CHARM.The catalog is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/431/773
| Testing Models of Stellar Evolution for Metal-poor Stars: An Interferometric-spectroscopic Orbit for the Binary HD 195987
We report spectroscopic and interferometric observations of themoderately metal-poor double-lined binary system HD 195987, with anorbital period of 57.3 days. By combining our radial-velocity andvisibility measurements, we determine the orbital elements and deriveabsolute masses for the components of MA=0.844+/-0.018Msolar and MB=0.6650+/-0.0079 Msolar,with relative errors of 2% and 1%, respectively. We also determine theorbital parallax, πorb=46.08+/-0.27 mas, corresponding toa distance of 21.70+/-0.13 pc. The parallax and the measured brightnessdifference between the stars in V, H, and K yield the component absolutemagnitudes in those bands. We also estimate the effective temperaturesof the stars as TAeff=5200+/-100 K andTBeff=4200+/-200 K. Together with detailedchemical abundance analyses from the literature giving [Fe/H]~-0.5(corrected for binarity) and [α/Fe]=+0.36, we use these physicalproperties to test current models of stellar evolution for metal-poorstars. Among the four that we considered, we find that no single modelfits all observed properties at the measured composition, although weidentify the assumptions in each one that account for the discrepancy,and we conclude that a model with the proper combination of assumptionsshould be able to reproduce all the radiative properties. Theindications from the isochrone fits and the pattern of enhancement ofthe metals in HD 195987 are consistent with this being a thick diskobject, with an age of 10-12 Gyr.
| Towards a fundamental calibration of stellar parameters of A, F, G, K dwarfs and giants
I report on the implementation of the empirical surface brightnesstechnique using the near-infrared Johnson broadband { (V-K)} colour assuitable sampling observable aimed at providing accurate effectivetemperatures of 537 dwarfs and giants of A-F-G-K spectral-type selectedfor a flux calibration of the Infrared Space Observatory (ISO). Thesurface brightness-colour correlation is carefully calibrated using aset of high-precision angular diameters measured by moderninterferometry techniques. The stellar sizes predicted by thiscorrelation are then combined with the bolometric flux measurementsavailable for a subset of 327 ISO standard stars in order to determineone-dimensional { (T, V-K)} temperature scales of dwarfs and giants. Theresulting very tight relationships show an intrinsic scatter induced byobservational photometry and bolometric flux measurements well below thetarget accuracy of +/- 1 % required for temperature determinations ofthe ISO standards. Major improvements related to the actual directcalibration are the high-precision broadband { K} magnitudes obtainedfor this purpose and the use of Hipparcos parallaxes for dereddeningphotometric data. The temperature scale of F-G-K dwarfs shows thesmallest random errors closely consistent with those affecting theobservational photometry alone, indicating a negligible contributionfrom the component due to the bolometric flux measurements despite thewide range in metallicity for these stars. A more detailed analysisusing a subset of selected dwarfs with large metallicity gradientsstrongly supports the actual bolometric fluxes as being practicallyunaffected by the metallicity of field stars, in contrast with recentresults claiming somewhat significant effects. The temperature scale ofF-G-K giants is affected by random errors much larger than those ofdwarfs, indicating that most of the relevant component of the scattercomes from the bolometric flux measurements. Since the giants have smallmetallicities, only gravity effects become likely responsible for theincreased level of scatter. The empirical stellar temperatures withsmall model-dependent corrections are compared with the semiempiricaldata by the Infrared Flux Method (IRFM) using the large sample of 327comparison stars. One major achievement is that all empirical andsemiempirical temperature estimates of F-G-K giants and dwarfs are foundto be closely consistent between each other to within +/- 1 %. However,there is also evidence for somewhat significant differential effects.These include an average systematic shift of (2.33 +/- 0.13) % affectingthe A-type stars, the semiempirical estimates being too low by thisamount, and an additional component of scatter as significant as +/- 1 %affecting all the comparison stars. The systematic effect confirms theresults from other investigations and indicates that previousdiscrepancies in applying the IRFM to A-type stars are not yet removedby using new LTE line-blanketed model atmospheres along with the updatedabsolute flux calibration, whereas the additional random component isfound to disappear in a broadband version of the IRFM using an infraredreference flux derived from wide rather than narrow band photometricdata. Table 1 and 2 are only available in the electronic form of thispaper
| The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
| Imaging polarimetry of AFGL 2591 and its associated reflection nebula
Near-infrared images of a 64 x 64 arc sec region surrounding the brightinfrared point source in AFGL 2591 reveal an area of extended emissionto its south and west. Polarimetric images and the relative color of thenebulosity confirm that the emission is produced by reflection of lightfrom the point source. These images cover a larger field of view thanprevious observations at H and K obtained by Forrest and Shure (1986)and show the nebular emission to extend further west. A newdetermination of the absolute position of the point source has also beenfound. The polarization of the point source and typical polarization ofthe nebula at J, H, and K all have a position angle perpendicular to thedirection of the blushifted high-velocity molecular outflow. Bothscattering and dichroic absorption by magnetically aligned grains in thedense cloud around the central source can contribute to the overallpolarization. A simple model is adopted to estimate the extinctionbetween the exciting star and both the surrounding nebula and theobserver. A young luminous central star, surrounded by a tilted, dense,dusty disk or torus, is consistent with the available data.
| Kinematical data of two samples of late-type stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977A&AS...27..267G&db_key=AST
| Star catalogs for the Washington and Richmond photographic zenith tubes.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973AJ.....78..642M&db_key=AST
| UBV Photometry of 173 PZT Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971PASP...83..177W&db_key=AST
| KURZE MITTEILUNG. Zur Expansion der Assoziation Cep III
Not Available
| Spectral Classification of Stars Noted on Case Objective Prism Plates. II
Not Available
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | ברבור |
| התרוממות ימנית: | 20h28m25.79s |
| סירוב: | +39°19'44.2" |
| גודל גלוי: | 6.961 |
| מרחק: | 291.545 פארסק |
| תנועה נכונה: | 13.6 |
| תנועה נכונה: | 15.4 |
| B-T magnitude: | 8.195 |
| V-T magnitude: | 7.063 |
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