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Multiperiodic RR Lyr Stars in the Center of the Galaxy

100%

Mizerski T.

tom Vol. 56, No. 4

307--320

This paper presents results of a fully automated search for multiperiodic RR Lyr stars in the center of the Galaxy. The search was carried out on OGLE-II database created by means of image subtraction method. I found more than 2700 RR Lyr stars with about 600 showing various kinds of multiperiodic behavior. Previous OGLE-I database contained only about 200 RR Lyr stars in the Galactic bulge, that is twelve times less than the current sample. There are two most interesting outcomes for the Galactic bulge sample: very high percentage of Blazhko stars and very low percentage of RRd stars. Blazhko effect was confirmed in about 25% of all RRab stars. This incidence rate is almost 2.5 times greater than in the Large Magellanic Cloud. On the other hand I discovered only 3 RRd stars which implies that the incidence rate of this type of variables is much smaller in the bulge sample than in the Magellanic Cloud RR Lyr stars.

The Optical Gravitational Lensing Experiment. Catalog of RR Lyr Stars from the Small Magellanic Cloud

100%

Soszyński I. , Udalski A. , Szymański M. , Kubiak M. , Pietrzyński G. , Woźniak P. , Żebruń K. , Szewczyk O. , Wyrzykowski Ł.

2002

tom Vol. 52, No. 4

369--396

We present the catalog of RR Lyrae stars from 2.4 square degrees of central parts of the Small Magellanic Cloud (SMC). The photometric data were collected during four years of the OGLE-II microlensing survey. Photometry of each star was obtained using the Difference Image Analysis (DIA) method. The catalog contains 571 objects, including 458 RRab, 56 RRc variables, and 57 double mode RR Lyr stars (RRd). Additionally we attach a list of variables with periods between 0.18-0.26 days, which are probably δ Sct stars. Period, BVI photometry, astrometry, amplitude, and parameters of the Fourier decomposition of the I-band light curve are provided for each object. We also present the Petersen diagram for double mode pulsators. We found that the SMC RR Lyr stars are fairly uniformly distributed over the studied area, with no clear correlation to any location. The most preferred periods for RRab and RRc stars are 0.589 and 0.357 days, respectively. We noticed significant excess of stars with periods of about 0.29 days, which might be second-overtone RR Lyr stars (RRe). The mean extinction free magnitudes derived for RRab stars are 18.97, 19.45 and 19.73 mag for the I, V and B-band, respectively. All presented data, including individual BVI observations, are available from the OGLE Internet archive.