Title:

                The PL relation of galactic carbon LPVs. The distance modulus to LMC
 Authors:

                Bergeat, J.; Knapik, A.; Rutily, B.
 Affiliation:

                Centre de Recherche Astronomique de Lyon (UMR 5574 du CNRS), Observatoire de Lyon, 9 avenue Charles
                Andre, F-69561 St-Genis-Laval cedex, France
 Journal:

                Astronomy and Astrophysics, v.332, p.L53-L56 (1998) (A&A Homepage)
 Publication Date:

                04/1998
 Origin:

                A&A
 A&A Keywords:

                STARS: AGB AND POST-AGB, STARS: CARBON, STARS: FUNDAMENTAL PARAMETERS,
                GALAXIES: DISTANCES
 Abstract Copyright:

                (c) 1998: Astronomy & Astrophysics
 Bibliographic Code:

                1998A&A...332L..53B


                                         Abstract

We present a period-luminosity (PL) diagram of 115 galactic carbon-rich long period variables (LPVs) observed by the HIPPARCOS
satellite, in the form of the <=ft(M_{K},log Pright ) relation. Our plot is compared to the diagram of carbon variables observed in the Large
Magellanic Cloud (LMC). Both diagrams are found very similar and three samples are delineated: long period variables close to the PL
relation of Feast et al. (1989), short period-overluminous variables and a few underluminous LPVs, respectively Samples 1, 2 and 3. The
used data were deduced from expectations of true parallaxes (Knapik et al. 1997) which are statistically free of the Lutz-Kelker effect. The
remaining bias due to the non-gaussian distribution of absolute magnitudes is avoided: a non-linear parametric method is applied in Sect. 4 to
the analysis of the PL relation for Sample 1 (72 LPVs). We obtain M_{K}=(-3.99+/-0.13)log P+(2.07+/-0.15), in good agreement with the
slope found for LMC variables by Reid et al. (1995). The LMC distance modulus then derived is mu =18.50+/-0.17. A well-defined upper
limit (ul) for long period stars in Sample 1 is found, with similar slopes in both the Galaxy (-4.85) and LMC (-4.72). No correction for
metallicity was applied to the results.

This research has made use of the Simbad database operated at CDS, Strasbourg, France.