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The Optical Gravitational Lensing Experiment. The OGLE-III Catalog of Variable Stars. VIII. Type II Cepheids in the Small Magellanic Cloud

Soszyński I., Udalski A., Szymański M. K., Kubiak M., Pietrzyński G., Wyrzykowski Ł., Ulaczyk K., Poleski R.

Acta Astronomica

2010

Vol. 60, No. 2

91--107

The eighth part of the OGLE-III Catalog of Variable Stars (OIII-CVS) contains type II Cepheids in the Small Magellanic Cloud (SMC). The sample consists of 43 objects, including 17 BL Her, 17 W Vir and 9 RV Tau stars (first examples ever found in the SMC). Seven stars have been classified as peculiar W Vir stars - a recently identified subclass of type II Cepheids. These stars have distinctive light curves, are brighter and bluer than the ordinary W Vir variables. We confirm that a large fraction of the peculiar W Vir stars are members of binary systems. Three type II Cepheids exhibit eclipsing variations superimposed on the pulsation light curves, and three other objects show long-period ellipsoidal variability. All stars with the indication of binarity display secondary periods which may be interpreted as amplitude and/or phase modulations of the pulsation light curves with periods equal to the orbital periods or half the orbital periods. We do not have any model for these modulations, however this phenomenon rules out a possibility of the optical blends of a pulsating star and a binary system. For each object the multi-epoch V- and I-band photometry collected over 8 or 13 years of observations and finding charts are available to the astronomical community from the OGLE Internet archive.

The All Sky Automated Survey. The Catalog of the Periodic Variable Stars in the Selected Fields

Pojmański G.

Acta Astronomica

1998

Vol. 48, No. 1

35--58

Results of the first two months of observations using the All Sky Automated Survey prototype camera are presented. More than 45 000 stars in 24 Selected Fields covering 140 square degrees were monitored a few times per night resulting in the I-band catalog containing 107 individual measurements. Period search revealed 126 variable stars brighter than 13 mag with periods less than 20d. Only 30 of them are known variable stars included in the General Catalogue of Variable Stars. The other 90 objects are newly detected variable stars - mainly eclipsing binaries (75%) and pulsating stars (17%). We estimate that completeness of the current catalogs of variable stars is smaller than 50% already for the stars brighter than 9 mag. The Catalog is accessible over the WWW: http://www.astrouw.edu.pl/~gp/asas/asas.html