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Hipparcos red stars in the HpV_T2 and V I_C systems
For Hipparcos M, S, and C spectral type stars, we provide calibratedinstantaneous (epoch) Cousins V - I color indices using newly derivedHpV_T2 photometry. Three new sets of ground-based Cousins V I data havebeen obtained for more than 170 carbon and red M giants. These datasetsin combination with the published sources of V I photometry served toobtain the calibration curves linking Hipparcos/Tycho Hp-V_T2 with theCousins V - I index. In total, 321 carbon stars and 4464 M- and S-typestars have new V - I indices. The standard error of the mean V - I isabout 0.1 mag or better down to Hp~9 although it deteriorates rapidly atfainter magnitudes. These V - I indices can be used to verify thepublished Hipparcos V - I color indices. Thus, we have identified ahandful of new cases where, instead of the real target, a random fieldstar has been observed. A considerable fraction of the DMSA/C and DMSA/Vsolutions for red stars appear not to be warranted. Most likely suchspurious solutions may originate from usage of a heavily biased color inthe astrometric processing.Based on observations from the Hipparcos astrometric satellite operatedby the European Space Agency (ESA 1997).}\fnmsep\thanks{Table 7 is onlyavailable 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/qcat?J/A+A/397/997
| New periodic variables from the Hipparcos epoch photometry
Two selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcos`unsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed.
| Long period variable stars: galactic populations and infrared luminosity calibrations
In this paper HIPPARCOS astrometric and kinematic data are used tocalibrate both infrared luminosities and kinematical parameters of LongPeriod Variable stars (LPVs). Individual absolute K and IRAS 12 and 25luminosities of 800 LPVs are determined and made available in electronicform. The estimated mean kinematics is analyzed in terms of galacticpopulations. LPVs are found to belong to galactic populations rangingfrom the thin disk to the extended disk. An age range and a lower limitof the initial mass is given for stars of each population. A differenceof 1.3 mag in K for the upper limit of the Asymptotic Giant Branch isfound between the disk and old disk galactic populations, confirming itsdependence on the mass in the main sequence. LPVs with a thin envelopeare distinguished using the estimated mean IRAS luminosities. The levelof attraction (in the classification sense) of each group for the usualclassifying parameters of LPVs (variability and spectral types) isexamined. Table only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/374/968 or via ASTRIDdatabase (http://astrid.graal.univ-montp2.fr).
| 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
| On the Variability of K5-M Stars
I investigate the Hipparcos Satellite photometry of K5-M stars to seethe pattern of activity of these stars. A few stars for which furtherstudy is desirable are identified.
| Classification and Identification of IRAS Sources with Low-Resolution Spectra
IRAS low-resolution spectra were extracted for 11,224 IRAS sources.These spectra were classified into astrophysical classes, based on thepresence of emission and absorption features and on the shape of thecontinuum. Counterparts of these IRAS sources in existing optical andinfrared catalogs are identified, and their optical spectral types arelisted if they are known. The correlations between thephotospheric/optical and circumstellar/infrared classification arediscussed.
| Pulsation and stability of RR Lyrae stars. 1: Instability strip
In order to provide a detailed analysis of RR Lyrae instability striptopology, an extensive grid of nonlinear, nonlocal, and time-dependentconvective models of RR Lyrae stars has been computed at fixed mass (M =0.65 solar mass) and chemical composition (Y = 0.299, Z = 0.001). Fourseries of envelope models at different luminosity levels (log(L/solarluminosity) = 1.81, 1.72, 1.61, 1.51) and on a large range of effectivetemperatures (5700 K less than Te less than 8000 K) have beeninvestigated. The nonlinear modal stability has been evaluated atlimiting amplitude for both the fundamental and the first overtone. Theequations governing both dynamical and convective interactions have beenintegrated in time until the initial perturbations and the nonlinearfluctuations due to superposition of higher order modes settled down.The theoretical observables obtained by the present survey (radius,luminosity, velocity and temperature amplitudes, periods) describe thepulsation characteristics of the models at full amplitude, hence theycan be properly compared with observations. A linear, nonadiabaticsurvey of the first three modes of RR Lyrae models has been alsocomputed to supply the static structure of the envelope to the nonlinearstability analysis. Several numerical simulations have been performed totest both the numerical accuracy (boundary conditions, time-step size,zoning) and the adequacy of the physical assumption (efficiency of theturbulent regime, artificial viscosity dependence, convective structureinitialization) adopted to describe the coupling between dynamical andconvective fields. The structure of the instability strip shows severalstriking features concerning the width in temperature of the regionwhere only the first overtone is unstable. Indeed, the fundamental blueedge, moving from higher to lower luminosity levels, becomes redder, incontrast to previous findings but in agreement with globular clustersobserved data. Moreover, using an improved treatment of the convectivetransport, the first-overtone red edge has been directly evaluated andhence also the width of the 'either-or' region (i.e., the region whereboth the fundamental and the first overtone are simultaneouslyunstable). It has been found that the periods of the nonlinearconvective models are systematically smaller than the correspondingperiods of both linear and nonlinear radiative models. The differencesbetween linear and nonlinear results are smaller than 2% of the period,however. This effect has been explained as a consequence of the changesinduced during the phases of maximum compression by the convectivetransport on the adiabatic exponent, and on the density inversionlocated in coincidence with the hydrogen ionization reigon.
| Statistical characteristics of the ten-micron silicate emission in M-type stars
The statistical characteristics of 10 micron silicate emission wereexamined for 1427 M-type stars in the catalog of the Two-Micron SkySurvey using the low-resolution spectra obtained by IRAS. Correlationswere examined of 10 micron silicate emission with the spectralclassification in the visual wavelength region, with near-infrared colorI - K, with a variability type, and with the period of variation. It wasfound that supergiants show silicate emission more frequently than dogiants. Silicate emission was found in stars of all three variabilitytypes: irregular, semiregular, and Mira variables. The proportion ofstars with silicate emission was found to be larger for Mira variables.Most of the Mira variables with periods of variation longer than about450 d were found to show silicate emission.
| Lunar occultations of IRAS point sources, 1991-2000
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1989ApJS...69..651C&db_key=AST
| Lunar occultations of IRAS point sources, 1986-1990
A complete listing is given for objects in the IRAS Point Source Catalogwhich will be occulted by the moon over the course of 1986-1990. A totalof 14,148 ASCII card images is encompassed by the complete listing ofobjects having geocentric events during this period. The resultscontained in this complete listing are illustrated in two of the presenttables for the brightest objects at 12 and 100 micron wavelengths.
| IRAS catalogues and atlases - Atlas of low-resolution spectra
Plots of all 5425 spectra in the IRAS catalogue of low-resolutionspectra are presented. The catalogue contains the average spectra ofmost IRAS poiont sources with 12 micron flux densities above 10 Jy.
| A redetermination of the Barnes-Evans relation for surface flux in the V band
Published BVRI photometry for stars with angular diameters establishedby lunar occultation or speckle and amplitude interferometry or fromtheir variability are compiled in tables and used to reevaluate thevisual-flux/color relation proposed by Barnes and Evans (1976). Theresults are presented in graphs and tables for red and blue stars, andthe relation derived is used to correct the UVBRI temperaturecalibration of Johnson (1966). Reasonable agreement is found with thetemperature and bolometric-correction scales of Code (1976) for the redstars, but not for the blue stars.
| The stellar component of the galaxy as seen by the AFGL infrared sky survey
The noise-limited magnitudes for the Air Force Geophysical Laboratory(AFGL) Infrared Sky Survey have been estimated by direct comparison withground-based observations. Using these limiting magnitudes, 'pruned'versions of the AFGL catalog have been generated. Infrared observationsof all the stellar objects seen at 11, 20, or 27 microns and astatistical sample of the stars seen only at 4 microns are reported.Analysis of the observations leads to estimates of the absolute 4 and 10microns magnitudes and space densities for the two clases of objects.The expected results from the Infrared Astronomical Satellite arereexamined.
| Spectrophotometry with a self-scanned silicon photodiode array. I - Instrumentation and reductions
A conventional spectrometer equipped with a Reticon photodiode array asa detector was used to demonstrate the applicability of such arrays toaccurate stellar spectrophotometry. Spectra were obtained at 42-Aresolution from 4650 to 10,000 A. High SNRs were obtainable to 10 mag,with typical integration times of a few minutes. Tests on Alpha Lyraedemonstrate the resultant flux distributions to be reduced to theabsolute flux scale to within + or - 0.025 mag (standard deviation of asingle observation) in zero point and internally precise to + or - 0.003mag.
| Stellar angular diameters and visual surface brightness. III - an improved definition of the relationship
The relation between visual surface brightness and (V-R)(0) is refinedby taking explicit account of the effects of limb darkening, by adding40 new stars to the previous calibration, introducing extensive new BVRIphotometry, and by incorporating additional angular-diametermeasurements. A tight correlation between the visual surface brightnessindex and (V-R)(0) was found to exist over the entire distribution;hence the conclusion is strengthened that (V-R)(0) can be used to infervisual surface brightness for all luminosity classes and spectral types,including S and C types.
| Derivation of angular diameters of stars from lunar occultations
A description is presented of the results obtained in the photoelectricobservations of occultations involving four stars. The considered starsinclude Eta Gem (ZC 946), Mu Gem (ZC 976), 187 B. Gem (ZC 1161), and 31Leo (ZC 1486). The theoretical principles of the studies are considered,taking into account point source occultations, the stellar diameter andthe influence of telescope aperture, and spectral effects. Observationaldata concerning the considered stars are presented in a table and anumber of graphs. It is pointed out that Mu Gem is a triple system.However, on account of their distances and their weakness the companionscannot affect the observed intensity curve. A combination of the deriveddiameter with the trigonometric parallax reported by Jenkins (1963)provides for the linear diameter of Mu Gem the result of 91 plus orminus 28 solar diameters.
| Photoelectric observations of lunar occultations.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975MNRAS.170..229H&db_key=AST
| 60th Name-List of Variable Stars
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Datos observacionales y astrométricos
| Constelación: | Libra |
| Ascensión Recta: | 15h32m15.14s |
| Declinación: | -23°52'48.6" |
| Magnitud Aparente: | 6.888 |
| Distancia: | 216.45 parsecs |
| Movimiento Propio en Ascensión Recta: | 16.9 |
| Movimiento Propio en Declinación: | -3.2 |
| B-T magnitude: | 8.807 |
| V-T magnitude: | 7.047 |
Catálogos y designaciones:
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