SCYON Abstract

Received on February 22 2006

CCD photometric search for peculiar stars in open clusters. VII. Berkeley 11, Berkeley 94, Haffner 15, Lynga 1, NGC 6031, NGC 6405, NGC 6834 and Ruprecht 130

AuthorsE. Paunzen(1), M. Netopil(1), I.Kh. Iliev(2), H.M. Maitzen(1), A. Claret(3), O.I. Pintado(4)
(1) Institute for Astronomy, University of Vienna, Türkenschanzstr. 17, A-1180 Wien, Austria
(2) Institute of Astronomy, National Astronomical Observatory, P.O. Box 36, BG-4700 Smolyan, Bulgaria
(3) Instituto de Astrofisica de Andalucia CSIC, Apartado 3004, 18080 Granada, Spain
(4) Departamento de Fisica, Facultad de Ciencias Exactas y Tecnologia, Universidad Nacional de Tucuman, Argentina - Consejo Nacional de Investigaciones Cientificas y Tecnicas de la Republica Argentina
Accepted byAstronomy & Astrophysics
Links Berkeley 11 / Berkeley 94 / Haffner 15 / Lynga 1 / NGC 6031 / NGC 6405 / NGC 6834 / Ruprecht 130


The detection of magnetic chemically peculiar (CP2) stars in open clusters of the Milky Way can give observational answers to many unsolved questions. One can study the influence of different galactic environments on the (non-)presence of peculiarities which has to be taken into account stellar evolution models. Furthermore it is still unknown if the CP2 phenomenon evolves, i.e. does the strength of the peculiarity feature at 520nm increase or decrease with age. We have observed eight young to intermediate aged open clusters in the Delta a photometric system. This intermediate band photometric system samples the depth of the 5200A flux depression by comparing the flux at the center with the adjacent regions with bandwidths of 110A to 230A. The Delta a photometric system is most suitable to detect CP2 stars with high efficiency, but is also capable of detecting a small percentage of non-magnetic CP objects. Furthermore, the groups of (metal-weak) lambda Bootis as well as classical Be/shell stars, can be successfully investigated. In addition, this photometric system allows to determine the age, reddening and distance modulus with an appropriate accuracy by fitting isochrones. Among the presented sample of eight galactic clusters, we have detected twenty three CP2, eight Be/Ae and eight metal-weak stars. Another six objects exhibit a peculiar behaviour which is most probable due to a none-membership, variability or duplicity. Fitting isochrones to our Delta a photometry yields an estimate of the age, reddening and distance which are in excellent agreement to already published values.