We present the catalog of RR Lyrae stars discovered in a 4.5 square degrees area in the central parts of the Large Magellanic Cloud (LMC). Presented sample contains 7612 objects, including 5455 fundamental mode pulsators (RRab), 1655 first-overtone (RRc), 272 second-overtone (RRe) and 230 double-mode RR Lyr stars (RRd). Additionally we attach a list of several dozen other short-period pulsating variables. The catalog data include astrometry, periods, BVI photometry, amplitudes, and parameters of the Fourier decomposition of the I-band light curve of each object.
We present density map of RR Lyr stars in the observed fields which shows
that the variables are strongly concentrated toward the LMC center. The
modal values of the period distribution for RRab, RRc and RRe stars 0 are
0.573, 0.339 and 0.276 days, respectively. The period-luminosity diagrams
for BVI magnitudes and for extinction insensitive
index WI are constructed. We provide the
logP-I, logP-V and
logP-WI relations for RRab, RRc and RRe stars. The
mean observed V-band magnitudes of RR Lyr stars in the LMC are 19.36
mag and 19.31 mag for ab and c types, respectively, while the extinction
free values are 18.91 mag and 18.89 mag.
We also found a large number of RR Lyr stars pulsating in two modes closely spaced in the power spectrum. These stars are believed to exhibit non-radial pulsating modes. We discovered three stars which simultaneously reveal RR Lyr-type and eclipsing-type variability. If any of these objects were an eclipsing binary system containing RR Lyr star, then for the first time the direct determination of the mass of RR Lyr variable would be possible.
We also provide a list of six LMC star clusters which contain RR Lyr stars. The richest cluster, NGC 1835, hosts 84 RR Lyr variables. The period distribution of these stars suggests that NGC 1835 shares features of Oosterhoff type I and type II groups. All presented data, including individual BVI observations and finding charts are available from the OGLE Internet archive.
PLEASE cite the following paper when using the data or referring to these OGLE results:
Soszynski et al., 2003, Acta Astron., 53, 93.
Any comments about the data and the form of their presentation are welcome as they can improve the future releases of catalogs of variable stars detected by OGLE-II collaboration. Send your messages to this address.