Luminosities and pulsational properties of RR Lyrae variables in the bar of the Large Magellanic Cloud
Abstract
New B,V CCD photometry in the standard Johnson system is presented for two fields (A and B) located close to the bar of the LMC and contained in fields 6 and 13 of the MACHO microlensing experiment. We detected 128 RR Lyrae variables in the two areas and obtained full coverage of the B and V light curves for 93 and 107 variables, respectively. The average apparent luminosity of the RR Lyrae's with complete V and B light curves is = 19.352+/-0.023 (52 stars) and =19.762+/-0.023 (48 stars) in field A, and <V(RR)=19.314+/-0.025 (41 stars) and =19.656+/-0.030 in field B (33 stars). The average apparent luminosity of the clump stars in the same fields is about 0.12 mag brighter than the RR Lyrae level (=19.223+/-0.003 and 19.200+/-0.003, in field A (5345 stars) and B (3639 stars), respectively). An estimate of the reddening was obtained from the colors of the edges of the instability strip defined by the RR Lyrae variables: E(B-V)=0.08+/-0.02, and 0.06+/-0.02 mag in field A and B. When coupled with the apparent luminosities of the RR Lyrae's and the absolute magnitude derived from the Baade-Wesselink and the statistical parallaxes methods these new reddening estimates lead to distance modulus for the LMC of 18.40+/-0.15. The present determination of the V luminosity of the clump when combined with OGLE-II o=0.89 mag, and corrected back to our new reddening values moves the clump distance modulus of the LMC to 18.42+/-0.07. All these values are only 1 sigma shorter than provided by the Population I distance indicators (e.g. the Cepheids), and allow to reconcile the short and long distance scale on a common value for the distance modulus of the LMC of 18.50+/-0.07.Keywords
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