Astron. Astrophys. Suppl. Ser.
Volume 128, Number 1, February II 1998
|Page(s)||19 - 28|
|Published online||15 February 1998|
IV. Fields 104A-E in 47 Tucanae
Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warsaw, Poland
2 Carnegie Observatories, Las Campanas Observatory, Casilla 601, La Serena, Chile
3 Department of Astronomy, University of Michigan, 821 Dennison Bldg., Ann Arbor, MI 48109-1090, U.S.A.
4 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, U.S.A.
Send offprint request to: J. Kaluzny
Accepted: 18 June 1997
Five fields located close to the center of the globular cluster NGC Tuc were surveyed in a search for variable stars. We present V-band light curves for 42 variables. This sample includes 13 RR Lyr stars – 12 of them belong to the Small Magellanic Cloud (SMC) and 1 is a background object from the galactic halo. Twelve eclipsing binaries were identified – 9 contact systems and 3 detached/semi-detached systems. Seven eclipsing binaries are located in the blue straggler region on the cluster color-magnitude diagram (CMD) and four binaries can be considered main-sequence systems. One binary is probably a member of the SMC. Eight contact binaries are likely members of the cluster and one is most probably a foreground star. We show that for the surveyed region of 47 Tuc, the relative frequency of contact binaries is very low as compared with other recently surveyed globular clusters. The sample of identified variables also includes 15 red variables with periods ranging from about 2 days to several weeks. A large fraction of these 15 variables probably belong to the SMC but a few stars are likely to be red giants in 47 Tuc. VI photometry for about 50 000 stars from the cluster fields was obtained as a by product of our survey.
Key words: globular clusters: individual: NGC 104 / star: variables: other / blue stragglers / binaries: eclipsing / HR diagram / Magellanic clouds
The photometric data presented in this paper are available in electronic form at the CDS, via anonymous ftp to cdsarc.u-strasbg.fr (18.104.22.168) or via http://cdsweb.u-strasbg.fr/Abstract.html
Based on observations collected at the Las Campanas Observatory of the Carnegie Institution of Washington.
© European Southern Observatory (ESO), 1998