D a & Broadband photometry of open clusters. Martin Netopil Institute of Astronomy, University of Vienna - Austria AIPW 2006 - Dubrovnik. Why open clusters?. They are physically related groups of stars held together by gravitational attraction and were formed at roughly the same time .
Da & Broadband photometryof open clusters
Institute of Astronomy, University of Vienna - Austria
AIPW 2006 - Dubrovnik
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Photometry offers an easy possibility for investigating large samples of CP stars, especially through the discovery of characteristic broadband absorption features, the most suitable of them located around 5200Å.
g1: 5027Å / 222Å
g2: 5205Å / 107Å
y: 5509Å / 120Å
The index (g1-y) shows an excellent correlation with (b – y) or (B – V)and can be used as an index for the effective temperature (Paunzen, Schnell, Maitzen 2005, 2006).
An y versus (g1-y) diagram (= cmd) for a cluster can then easily sorts out non-members. Assuming that all stars exhibit the same interstellar reddening, peculiar objects deviate from the normality line more than 3s.
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Netopil, Paunzen, Maitzen et al. (2006) submitted
advantages: Isochrones available (Claret et al. 2003, Claret 2004);
accurate photometry (~10 frames each => time consuming);
reduction „relative“ simple using available packages (apphot, daophot); no standard fields necessary
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Netopil, Maitzen, Paunzen et al. (2006)
reduction „relative“ simple using available packages (apphot, daophot)
„problems“: standard transformation, atmospheric extinction
observing strategy: all observations at low airmass back-to-back
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