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The Baade-Wesselink method and the distances to RR Lyrae stars. VI - The field stars RS Bootis, TW Herculis, VY Serpentis, and UU Virginis, and the absolute magnitudes of RR Lyrae stars
Simultaneous BVK photometry and radial velocities from high-resolutionspectroscopy are used to derive distances and absolute magnitudes forthree metal-rich RR Lyrae stars: RS Boo, TW Her, and UU Vir, using thesurface brightness version of the Baade-Wesselink method. New Kphotometry and previously published optical photometry and radialvelocities are used to perform the same analysis upon the extremevelocity metal-poor RR Lyrae variable VY Ser. The results of otherdeterminations of (MV)RR are critically reevaluated to see whether RRLyrae stars are less luminous than 0.6 mag. The results support therecent proposal that there may be a simple period-(MK) relation that isindependent of metallicity and temperature effects. Such a relationshipwould provide an improved estimate for the distance to the Galacticcenter or for any high-reddening region. The age of the RR Lyrae-richglobular cluster M5 is estimated at (18 + or - 3) x 10 to the 9th yr.
| The Baade-Wesselink method and the distances to RR Lyrae stars. I - The field star VY Serpentis
The desirability and feasibility of determining distances to globularclusters, independently of field star calibrations using theBaade-Wesselink method is discussed. As a preliminary test of themethod, simultaneous, accurate photometric and radial velocity data forthe cool, lightly reddened field RR Lyrae variable VY Serpentis arepresented. The data are used to solve for the star's radius anddistance, using two versions of the Baade-Wesselink method that eachallow for the star's low metallicity and its changing gravity. For bothversions of the method, a phase difference of Delta phi approximately0.075, between the photometric and spectroscopic radii, is found. It isconcluded that the problem arises not from the method or its basicassumptions, but rather from the choice of a star with strong convectionwhich has not been properly taken into account.
| A Finding List of Early-Type Stars in Regions of Intermediate Galactic Latitude
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969ApJ...157..327U&db_key=AST
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Osservazione e dati astrometrici
| Costellazione: | Serpente |
| Ascensione retta: | 15h29m26.76s |
| Declinazione: | +01°50'37.1" |
| Magnitudine apparente: | 8.781 |
| Distanza: | 210.526 parsec |
| Moto proprio RA: | 4.6 |
| Moto proprio Dec: | 1.3 |
| B-T magnitude: | 9.268 |
| V-T magnitude: | 8.822 |
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