Photometric Variability of the mCP Star CS Vir: Evolution of the Rotation Period

What is it about?

The paper shows that high-quality data taken from the STEREO satellite between 2007 and 2011 are quite sufficient to precisely determine the rotation period of a CP star. By using the five years of photometric data set, the period of CS Vir iss improved to be 9.29572(12) days. We also show based on the examination of the data from the STEREO satellite and archives that CS Vir has an explicit period variation in its O-C diagram. The paper indicates that the period has been gradually increasing over years, and that the rotation of the star has slowed down by 0.66(8) seconds per year. According to this period variation, rotation deceleration in CS Vir might be a result of rotational braking in outer layers caused by angular momentum loss via magnetically-confined stellar wind.

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Why is it important?

A vast majority of the discovered CP stars both in our galaxy and others do not exhibit a light curve or a period variation. However, there is a small number of CP stars such as SX Ari, V901 Ori and CU Vir whose rotation periods slightly or excessively have changed over decades. In this paper, we show based on the examination of the data from the STEREO satellite and archives that CS Vir has an explicit period variation in its O-C diagram. There are numerous compiled ground- and space-based catalogues with hundreds of CP stars. There are also several studies related to surface structures and pulsational behaviour of CP stars. However, few studies have been performed to achieve a better understanding of the period changes of these variables, and almost none of them are based on space-based missions. Therefore, this investigation is quite important in terms of contributing to studies on the period evolution of CP stars.