New variable stars in open clusters

Abstract

Abstract. We present high precision CCD photometry of 1791 objects in 20 open clusters with an age of 10 Myr to 1 Gyr. These observations were performed within the ∆a photometric system which is primarily used to detect chemically peculiar stars of the upper main sequence. Time bases range from 30 min up to 60 days with data from several nights. We describe the time series analysis reaching a detection limit of down to 0.006 mag for apparent variability. In total, we have detected 35 variable objects of which four are not members of their corresponding clusters. The variables cover the entire Hertzsprung-Russell diagram, hence they are interesting targets for follow-up observations.

Variable stars in the field of open cluster NGC 6819 - II

“…A number of projects focus specifically on open clusters (e.g. Kaluzny, Krzemiński & Mazur 1996; Mochejska & Kaluzny 1999; Mochejska, Stanek & Kaluzny 2003; Paunzen et al 2004). These observations often provide the first time‐series data available on cluster in this magnitude range (and hence spectral type).…”

uvbyFCAPT Photometry of the Magnetic Chemically Peculiar Stars 36 Aurigae, HR 2722, 13 Andromedae, and HD 220147

“…Hipparcos photometry (Adelman et al 2000) shows that its amplitude (0.05 mag) is greater than stars of similar spectral type and that it is a mCP star rather than a HgMn star. In fact, its variability was discovered using these data (see Paunzen & Maitzen 1998), and a period of 1.47946 days was indicated (see Celestia 2000, ESA 1998.…”

Studies of FCAPTUVBY photometry for the mCP stars HD 32966, HD 35298, HD 68292, HD 93226, HD 171247, HD 217833, HD 220147, and HD 223358

“…It is listed as a B9 Si star in the Renson (1991) catalogue. Hipparcos photometry (ESA 1998) was analyzed by Paunzen & Maitzen (1998) who discovered a period of 5.7426 days. Koen (2001) reanalyzed the Hipparcos epoch photometric data and obtained two frequencies of $$$ {f}_1=0.17423\kern0.3em {d}^{-1} $$$ and $$$ {f}_2=3.27613\kern0.3em {d}^{-1} $$$.…”