Preliminary study of the moderately cool chemically peculiar star BS Circini

TL;DR

This study models the light variations of the chemically peculiar star BS Cir, revealing a two-spot configuration, spectral line variations, and a gradually increasing rotation period likely due to magnetic precession.

Contribution

It introduces a successful two-spot model for BS Cir's light variations and discusses the star's spectral line changes and period increase due to magnetic effects.

Findings

Successful two-spot light variation model fitting nine light curves

Confirmed the star's period is increasing at a rate of 5.4×10^-9

Detected minor secular changes in light curve shape

Abstract

BS Cir is a representative of moderately cool magnetic chemically peculiar stars which displays very strong light variations in Stroemgren index c1 indicating large changes in the height of the Balmer jump. We present two-spot model of light variations fitting successfully all of nine light curves obtained in the spectral region 335-750 nm. We also discuss the nature of the observed variations of intensities of Fe, Cr, Ti, Si, Mg and RE spectral lines and possible mechanisms matching the observed light variations. It was confirmed that the observed period of BS Cir 2.204 d is rising with the rate of dP/dt=5.4(4)x10^-9. The found minor secular changes in the shape of light curve should be compatible with the period changes caused by precessional motion due to magnetic distortion of the star.