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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).
| Period-Luminosity-Colour distribution and classification of Galactic oxygen-rich LPVs. I. Luminosity calibrations
The absolute K magnitudes and kinematic parameters of about 350oxygen-rich Long-Period Variable stars are calibrated, by means of anup-to-date maximum-likelihood method, using Hipparcos parallaxes andproper motions together with radial velocities and, as additional data,periods and V-K colour indices. Four groups, differing by theirkinematics and mean magnitudes, are found. For each of them, we alsoobtain the distributions of magnitude, period and de-reddened colour ofthe base population, as well as de-biased period-luminosity-colourrelations and their two-dimensional projections. The SRa semiregulars donot seem to constitute a separate class of LPVs. The SRb appear tobelong to two populations of different ages. In a PL diagram, theyconstitute two evolutionary sequences towards the Mira stage. The Mirasof the disk appear to pulsate on a lower-order mode. The slopes of theirde-biased PL and PC relations are found to be very different from theones of the Oxygen Miras of the LMC. This suggests that a significantnumber of so-called Miras of the LMC are misclassified. This alsosuggests that the Miras of the LMC do not constitute a homogeneousgroup, but include a significant proportion of metal-deficient stars,suggesting a relatively smooth star formation history. As a consequence,one may not trivially transpose the LMC period-luminosity relation fromone galaxy to the other Based on data from the Hipparcos astrometrysatellite. Appendix B is only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Photoelektrische UBV-Photometrie des Sternes RV Equulei.
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| Multicolor television photometry of T Tauri stars. I - Observational technique and preliminary results. II - The nature of variability in T Tauri stars
Results are presented for television observations of 17 T Tauri starsusing a seven-color photometric system. Three types of continuumvariability are distinguished: brightness changes in red light,simultaneous active brightness changes in all spectral regions, andbrightness changes that are more pronounced in the UV than in the redregion. The stars characterized by the first type of variability areshown to have significantly higher bolometric magnitudes than the starsexhibiting the other types, and discrepancies between observed energydistributions and spectral types are tentatively attributed toabsorption of light in circumstellar shells. The absolute energy fluxesemitted by the stellar photospheres in the visible region of thespectrum are calculated along with the Balmer-continuum, H-alpha, andH-beta fluxes originating from the circumstellar gas shells. It is foundthat the type of stellar variability depends on circumstellar-shellluminosity in the Balmer continuum.
| An infrared survey of RW Aurigae stars
An infrared photometric survey of 89 RW Aur type variables in bothhemispheres has been made. JHKL magnitudes and colors are listed. The RWAur variables include a small number of highly reddened late-type stars.All T Tauri and hot Orion population stars show infrared excesses andthe infrared properties mark certain field stars as being young. Thegreatest infrared excesses are found for A and F stars while youngvariable B stars usually show no excesses. The location of the RW Aurstars in the two-color H-K, K-L diagram favor dust re-radiation overfree-free emission as the mechanism responsible for the infrared excess.A weak correlation of H-K with emission class links the occurrence ofcircumstellar dust and gas shells.
| Absolute Proper Motions of 21 Variables of the RW Aur Type.
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Datos observacionales y astrométricos
| Constelación: | Pequeño Caballo |
| Ascensión Recta: | 21h14m53.59s |
| Declinación: | +08°59'37.2" |
| Magnitud Aparente: | 9.155 |
| Movimiento Propio en Ascensión Recta: | 8.9 |
| Movimiento Propio en Declinación: | -14.4 |
| B-T magnitude: | 10.546 |
| V-T magnitude: | 9.27 |
Catálogos y designaciones:
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