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מאמרים קשורים
Galactic model parameters for field giants separated from field dwarfs by their 2MASS and V apparent magnitudes
We present a method which separates field dwarfs and field giants bytheir 2MASS and V apparent magnitudes. This method is based onspectroscopically selected standards and is hence reliable. We appliedit to stars in two fields, SA 54 and SA 82, and we estimated a full setof Galactic model parameters for giants including their total localspace density. Our results are in agreement with the ones given in therecent literature.
| Effective temperature scale and bolometric corrections from 2MASS photometry
We present a method to determine effective temperatures, angularsemi-diameters and bolometric corrections for population I and II FGKtype stars based on V and 2MASS IR photometry. Accurate calibration isaccomplished by using a sample of solar analogues, whose averagetemperature is assumed to be equal to the solar effective temperature of5777 K. By taking into account all possible sources of error we estimateassociated uncertainties to better than 1% in effective temperature andin the range 1.0-2.5% in angular semi-diameter for unreddened stars.Comparison of our new temperatures with other determinations extractedfrom the literature indicates, in general, remarkably good agreement.These results suggest that the effective temperaure scale of FGK starsis currently established with an accuracy better than 0.5%-1%. Theapplication of the method to a sample of 10 999 dwarfs in the Hipparcoscatalogue allows us to define temperature and bolometric correction (Kband) calibrations as a function of (V-K), [m/H] and log g. Bolometriccorrections in the V and K bands as a function of T_eff, [m/H] and log gare also given. We provide effective temperatures, angularsemi-diameters, radii and bolometric corrections in the V and K bandsfor the 10 999 FGK stars in our sample with the correspondinguncertainties.
| Catalogue and bibliography of the UV Cet-type flare stars and related objects in the solar vicinity
This new catalogue of flare stars includes 463 objects. It containsastrometric, spectral and photometric data as well as information on theinfrared, radio and X-ray properties and general stellar parameters.From the total reference list of about 3400 articles, partial listsselected by objects, authors, key words and by any pairs of thesecriteria can be obtained Tables 1, 2 and 3 are only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html.
| 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.
| 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
| A model of zonal spottedness for red dwarf stars
Not Available
| Photometric and spectroscopic studies of cool stars discovered in EXOSAT X-ray images. III. Photometric properties.
We present high-precision UBV(RI)_c_ photometry for a sample of activestars detected serendipitously by the EXOSAT satellite. Fourteenobjects, out of 47 likely optical counterparts, turned out to be clearlyvariable, with periods in the range 1-8 days, including a newlydiscovered eclipsing binary. For most of them the optical variability isconsistent with the presence of photospheric cool spots. We have usedour multicolour photometry to estimate spectral classifications anddistances. The derived distances indicate that some of the observedstars are previously unidentified nearby (d<=25pc) M dwarfs. Whencombined with the results of high resolution spectroscopy, ourphotometric observations allow us to investigate the stellar content ofthe selected X-ray sample. Young stars and RS CVn-type binaries appearto constitute a large fraction of the selected sample.
| ROSAT X-Ray Observations of the 2A 0335+096 Cluster of Galaxies
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...455..497I&db_key=AST
| Photometric and spectroscopic studies of cool stars discovered in EXOSAT X-ray images II. Lithium abundances
We present high-resolution spectra in the Li I 6708 A region, andmulticolor photometry, for a sample of active stars detectedserendipitously by the EXOSAT satellite. We analyse the spectral datawith a spectral synthesis code and derive Li abundances, rotation ratesand metallicities. We use our multicolor photometry to infer thespectral classification and distance of the stars in the sample. Thederived Li abundances are compared with those of various samplesincluding randomly selected field stars, RS CVn binaries, and clustersand associations of different ages. We show that Li per se is notsufficient to determine unambiguously the nature and evolutionary stateof the sample stars, but can provide useful constraints if used inconjunction with other diagnostics like binarity, spectral class,rotation rate and X-ray luminosity. We show in particular that at leastone third of the EXOSAT sample is constituted by young stars, with agescomparable to or younger than the Pleiades (~7x10^7^ yr). Another thirdconsists of RS CVn binaries, while the classification of the remainingobjects is uncertain. They could be either young stars or evolved activebinaries. We argue that a similar composition also applies to the sampleof X-ray stellar sources detected serendipitously by the EinsteinObservatory.
| The EXOSAT high Galactic latitude survey
This study presents a survey of serendipitous sources performed in thevery soft X-ray band (0.05-2.0 keV) using the Exosat imaging telescopes.It covers 783 sq deg of high Galactic latitude sky and includes 210serendipitous sources which define a complete (flux-limited) sample. Twohundred of the 210 detected sources are identified via extensive opticaland radio observations together with cross-correlations with catalogs ofknown objects. The log N-log S relation was found to be consistent withthat of the Einstein extended Medium-Sensitivity Survey (EMSS) and withthe 'Euclidean' value of 1.5. The normalization of the relation is astrong function of the assumed spectral slope of AGN. It is inferredfrom the consistency with the EMSS results that the average (energy)slope of extragalactic sources in the soft X-ray band is very steep(approximately 1.5). An analysis of the association between AGNdetection and Galactic N(H) also shows that the average slope is steepand inconsistent with the canonical value of 0.7.
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לינקים קשורים
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משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | שור |
| התרוממות ימנית: | 03h39m04.46s |
| סירוב: | +09°39'10.2" |
| גודל גלוי: | 9.043 |
| תנועה נכונה: | 9.2 |
| תנועה נכונה: | -34.9 |
| B-T magnitude: | 9.841 |
| V-T magnitude: | 9.109 |
קטלוגים וכינוים:
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