A photometric long-term study of CP stars in open clusters

TL;DR

This study analyzes long-term photometric data of 27 chemically peculiar stars in open clusters to determine their rotational periods and variability, providing new insights into stellar magnetic activity and surface mapping potential.

Contribution

It presents the first detection of variability in 14 CP stars and refines rotational periods for others, using a comprehensive six-year dataset combined with existing data.

Findings

Established variability in 14 CP stars for the first time.

Refined rotational periods for 2 stars through data merging.

Confirmed periods for 6 stars; no significant variations for 5 stars.

Abstract

Photometric variability of chemically peculiar (CP) stars of the upper main sequence is closely connected to their local stellar magnetic field and their rotational period. Long term investigations, as presented here, help us to identify possible stellar cycles (as in the Sun). Furthermore, these data provide a basis for detailed surface mapping techniques. Photoelectric Stroemgren uvby time series for 27 CP stars within the boundaries of open clusters are presented. In addition, Hipparcos photometric data (from 1989 to 1993) are used for our analysis. Our observations cover a time period of about six years (1986 to 1992) with typically fifteen measurements for each objects. These observations help us to determine the rotational periods of these objects. A standard reduction procedure was applied to the data. When possible, we merged our data sets with already published ones to obtain a more significant result. A detailed time series analysis was performed, involving five different methods to minimize spurious detections. We established, for the first time, variability for fourteen CP stars. For additional two stars, a merging of already published data sets, resulted in more precise periods, whereas for six objects, the published periods could be confirmed. Last, but not least, no significant variations were found for five stars. Apart from six stars, all targets seem to be members of their host open clusters.