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The Clusters AgeS Experiment (CASE): Variable Stars in the Globular Cluster 47 Tucanae

Kaluzny J., Rozyczka M., Pych W., Krzeminski W., Zloczewski K., Narloch W., Thompson I. B.

Acta Astronomica

2013

Vol. 63, No. 3

309--322

Based on over 5400 BV images of 47 Tuc collected between 1998 and 2010 we obtained light curves of 65 variables, 19 of which are newly detected objects. New variables are located mostly just outside the core in a region poorly studied by earlier surveys of the cluster. Among them there are four detached eclipsing binaries and five likely optical counterparts of X-ray sources. Two detached systems are promising targets for follow-up observations. We briefly discuss properties of the most interesting new variables.

BVI CCD Photometry of the Globular Cluster 47 Tuc

Kaluzny J., Wysocka A., Stanek K. Z., Krzemiński W.

Acta Astronomica

1998

Vol. 48, No. 3

439--453

We present BVI photometry for about 16000 stars from a 220 square arcmin field centered 8 arcmin East of the center of 47 Tuc. We have identified eight likely blue stragglers located in the outer parts of the cluster. Four of these objects are easy targets for spectroscopic studies with ground-based telescopes. Six candidates for blue horizontal branch stars were identified. However, it is possible that all or most of them belong in fact to the SMC halo. One faint blue star being candidate for a cataclysmic variable was found close to the cluster center. The average I-band magnitude for stars forming the red giant branch clump is determined at I0=13.09±0.005 mag. This in turn implies distance modulus of the cluster (m-M)0,47Tuc=13.32±0.03±0.036 mag (statistical plus systematic error), if we adopt MI,m=-0.23±0.03 mag for the average absolute luminosity of Hipparcos-calibrated clump giants, following Paczyński and Stanek and Stanek and Garnavich. This distance modulus of 47 Tuc is lower by 0.2-0.25 mag than its recent estimates based on Hipparcos parallaxes for subdwarfs. We discuss possible reasons for this discrepancy. The photometric data are available through the anonymous ftp service.