EDP Sciences
Free access
Volume 410, Number 1, October IV 2003
Page(s) 323 - 335
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20031198

A&A 410, 323-335 (2003)
DOI: 10.1051/0004-6361:20031198

A search for planets in the old open cluster NGC 6791

H. Bruntt1, F. Grundahl1, B. Tingley1, S. Frandsen1, P. B. Stetson2 and B. Thomsen1

1  Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, 8000 Aarhus C, Denmark
2  Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics, National Research Council, 5071 West Saanich Road, Victoria, British Columbia V9E 2E7, Canada

(Received 2 May 2003 / Accepted 31 July 2003 )

We describe the results of a search for transit-like events caused by giant planets occulting stars in the old, metal-rich open cluster NGC 6791 based on BVI-colour photometry from eight nights of observations with the 2.54 m Nordic Optical Telescope. To extract the light curves we have used both PSF photometry (DAOPHOT) and the difference imaging technique (ISIS). We have re-analyzed observations from earlier campaigns to search for multiple transits, determine periods of long-period variables, and detect eclipsing binaries. We confirm 20 known variables and have discovered 22 new low-amplitude variables with amplitudes in the range 7-40 mmag and periods 1-16 days. We have found the primary and secondary eclipses of two eclipsing binaries based on the new and older photometric campaigns. The search for transit-like events has turned up a few single-transit candidates. The transit depths are 10 mmag in both the V and I filters over periods of 1.0-2.5 hours, but future observations are required to see whether identical transit-like events recur in these same stars.

Key words: stars: planetary systems -- stars: binaries: eclipsing -- stars: variables: general -- open clusters and associations: individual: NGC 6791

Offprint request: H. Bruntt, bruntt@phys.au.dk

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© ESO 2003