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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.
| An Observational Pursuit for Population III Stars in a Lyα Emitter at z = 6.33 through He II Emission
We present a very deep near-infrared spectroscopic observation of astrong Lyα emitter at z=6.33, SDF J132440.6+273607, which we usedto search for He II λ1640. This emission line is expected if thetarget hosts a significant number of Population III stars. Even after 42ks of integration with the Subaru/OHS spectrograph, no emission-linefeatures are detected in the J and H bands, which confirms that SDFJ132440.6+273607 is neither an active galactic nucleus nor a low-zemission-line object. We obtained a 2 σ upper limit of9.06×10-18 ergs s-1 cm-2 on theHe II λ1640 emission-line flux, which corresponds to a luminosityof 4.11×1042 ergs s-1. This upper limit onthe He II λ1640 luminosity implies that the upper limit on thePopulation III star formation rate is in the range 4.9-41.2Msolar yr-1 if Population III stars suffer no massloss and in the range 1.8-13.2 Msolar yr-1 ifstrong mass loss is present. The nondetection of He II in SDFJ132440.6+273607 at z=6.33 may thus disfavor weak feedback models forPopulation III stars.Based on data collected at the Subaru Telescope, which is operated bythe National Astronomical Observatory of Japan.
| Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS
Radial velocities have been determined for a sample of 2930 B2-F5 stars,95% observed by the Hipparcos satellite in the north hemisphere and 80%without reliable radial velocity up to now. Observations were obtainedat the Observatoire de Haute Provence with a dispersion of 80Ä,mm(-1) with the aim of studying stellar and galactic dynamics.Radial velocities have been measured by correlation with templates ofthe same spectral class. The mean obtained precision is 3.0 km s(-1)with three observations. A new MK spectral classification is estimatedfor all stars. Based on observations made at the Haute ProvenceObservatory, France and on data from The Hipparcos Catalogue, ESA.Tables 4, 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr or viahttp://cdsweb.u-strasbg.fr/Abstract.htm
| 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.
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Pozíciós és asztrometriai adatok
| Csillagkép: | Ökörhajcsár |
| Rektaszcenzió: | 14h36m57.10s |
| Deklináció: | +27°50'10.5" |
| Vizuális fényesség: | 8.549 |
| Távolság: | 215.517 parszek |
| RA sajátmozgás: | -10.3 |
| Dec sajátmozgás: | -1.1 |
| B-T magnitude: | 8.849 |
| V-T magnitude: | 8.574 |
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