Magnetic field and radial velocities of the star Chi Draconis A

TL;DR

This study reports the detection of a weak, variable magnetic field on Chi Draconis A, along with refined radial velocity measurements that suggest possible magnetic spots, pulsations, or an orbiting planet.

Contribution

First high-resolution spectropolarimetric observations confirming a weak magnetic field on Chi Draconis A and refined orbital parameters with indications of additional influences.

Findings

Magnetic field varies with a 23-day period.

Radial velocities show deviations from the orbital curve.

Potential presence of magnetic spots, pulsations, or a planet.

Abstract

We present high-resolution spectropolarimetric observations of the spectroscopic binary Chi Dra. Spectral lines in the spectrum of the main component Chi Dra A show variable Zeeman displacement, which confrms earlier suggestions about the presence of a weak magnetic field on the surface of this star. Within about 2 years of time base of our observations, the longitudinal component BL of the magnetic field exhibits variation from -11.5 +/- 2.5 G to +11.1 +/- 2.1 G with a period of about 23 days. Considering the rotational velocity of Chi DraA in the literature and that newly measured in this work, this variability may be explained by the stellar rotation under the assumption that the magnetic field is globally stable. Our new measurements of the radial velocities (RV) in high-resolution I-spectra of Chi Dra A refined the orbital parameters and reveal persistent deviations of RVs from the orbital curve. We suspect that these deviations may be due to the in uence of local magnetically generated spots, pulsations, or a Jupiter-size planet orbiting the system.