Strömgren photometry of the open clusters NGC 6134 and NGC 3680^*

¹ Institute for Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
² Theoretical Astrophysics Center, Danmarks Grundforskningsfond, Aarhus University, DK-8000 Aarhus C, Denmark
³ Nordic Optical Telescope Apartado 474, Santa Cruz de La Palma, E-38700, Spain

Send offprint request to: H. Bruntt

Received: 17 May 1999
Accepted: 9 June 1999

Abstract

We present Strömgren photometry of the two southern open clusters NGC 6134 and NGC 3680. The field of NGC 6134 was observed with different shifts of the telescope and rotations of the CCD camera in order to detect and remove any large scale flat field errors using the technique described by Andersen et al. (1995). By using calibrations of the Ström gren indices we find the metallicity and interstellar reddening of the clusters: For NGC 6134 the results are [Fe/H] and and for NGC 3680 we find and . When comparing the observed colour-magnitude diagrams theoretical isochrones we find that models which include overshooting in the convective cores agree with the extended hook after the turnoff. From the isochrone fit we find ages of Gyr and Gyr for NGC 6134 and NGC 3680 respectively. Strömgren  photometry of six known δ Scuti stars in NGC 6134 is presented.