Title:

                The absolute magnitudes of RR Lyraes from HIPPARCOS parallaxes and proper motions
 Authors:

                Fernley, J.; Barnes, T. G.; Skillen, I.; Hawley, S. L.; Hanley, C. J.; Evans, D. W.; Solano, E.; Garrido, R.
 Affiliation:

                AA(IUE Observatory, P.O. Box 50727, E-28080 Madrid, Spain (jaf or wji oresm@vilspa.esa.es)), AB(McDonald
                Observatory, University of Texas, Austin, Texas 78712, USA (tgb@astro.as.utexas.edu)), AC(IUE Observatory,
                P.O. Box 50727, E-28080 Madrid, Spain (jaf or wji oresm@vilspa.esa.es)), AD(Department Physics and
                Astronomy, Michigan State University, E. Lansing, Michigan 48824, USA (slh orchris@pillan.pa.msu.edu)),
                AE(Department Physics and Astronomy, Michigan State University, E. Lansing, Michigan 48824, USA (slh
                orchris@pillan.pa.msu.edu)), AF(Royal Greenwich Observatory, Madingley Rd, Cambridge CB3 OHA, England
                (dwe@ast.cam.ac.uk)), AG(IUE Observatory, P.O. Box 50727, E-28080 Madrid, Spain (jaf or wji
                oresm@vilspa.esa.es)), AH(Inst. Astrofisica de Andalucia, Apdo 3004, E-18080 Granada, Spain
                (garrido@iaa.es))
 Journal:

                Astronomy and Astrophysics, v.330, p.515-520 (1998) (A&A Homepage)
 Publication Date:

                02/1998
 Origin:

                A&A
 A&A Keywords:

                STARS: VARIABLES: RR LYRAES, GALAXY: GLOBULAR CLUSTERS, GALAXIES: MAGELLANIC
                CLOUDS
 Abstract Copyright:

                (c) 1998: Astronomy & Astrophysics
 Bibliographic Code:

                1998A&A...330..515F


                                         Abstract

We have used HIPPARCOS proper motions and the method of Statistical Parallax to estimate the absolute magnitude of RR Lyrae stars. In
addition we used the HIPPARCOS parallax of RR Lyrae itself to determine it's absolute magnitude. These two results are in excellent
agreement with each other and give a zero-point for the RR Lyrae M_v,[Fe/H] relation of 0.77+/-0.15 at [Fe/H]=-1.53. This zero-point is in
good agreement with that obtained recently by several groups using Baade-Wesselink methods which, averaged over the results from the
different groups, gives M_v = 0.73+/-0.14 at [Fe/H]=-1.53. Taking the HIPPARCOS based zero-point and a value of 0.18+/-0.03 for the
slope of the M_v,[Fe/H] relation from the literature we find firstly, the distance modulus of the LMC is 18.26+/-0.15 and secondly, the mean
age of the Globular Clusters is 17.4+/-3.0 GYrs. These values are compared with recent estimates based on other "standard candles" that
have also been calibrated with HIPPARCOS data. It is clear that, in addition to astrophysical problems, there are also problems in the
application of HIPPARCOS data that are not yet fully understood.

Table 1, which contains the basic data for the RR Lyraes, is available only at CDS. It may be retrieved via anonymous FTP at
cdsarc.u-strasbg.fr (130.79.128.5) or via the Web at http://cdsweb.u-strasbg.fr/Abstract.html