Magnetic fields and differential rotation on the pre-main sequence III: The early-G star HD 106506

TL;DR

This study combines photometry and spectropolarimetry to map the magnetic fields and differential rotation of the pre-main sequence star HD 106506, revealing significant azimuthal magnetic fields and solar-like differential rotation much stronger than the Sun's.

Contribution

First detailed magnetic and rotational mapping of HD 106506 using Zeeman Doppler imaging, showing prominent polar spots and strong differential rotation in a pre-main sequence star.

Findings

HD 106506 has a photometric period of ~1.416 days.

The star exhibits a significant azimuthal magnetic field.

Differential rotation is about four times that of the Sun.

Abstract

We present photometry and spectropolarimetry of the pre-main sequence star HD 106506. A photometric rotational period of ~1.416 +/- 0.133 days has been derived using observations at Mount Kent Observatory (MKO). Spectropolarimetric data taken at the 3.9-m Anglo-Australian Telescope (AAT) were used to derive spot occupancy and magnetic maps of the star through the technique of Zeeman Doppler imaging (ZDI). The resulting brightness maps indicate that HD 106506 displays photospheric spots at all latitudes including a predominant polar spot. Azimuthal and radial magnetic images of this star have been derived, and a significant azimuthal magnetic field is indicated, in line with other active young stars. A solar-like differential rotation law was incorporated into the imaging process. Using Stokes I information the equatorial rotation rate, $\Omega_{eq}$, was found to be 4.54 +/- 0.01 rad/d, with a photospheric shear $\delta\Omega$ of $0.21_{-0.03}^{+0.02}$ rad/d. This equates to an equatorial rotation period of ~1.39 +/- 0.01 days, with the equatorial region lapping the poles every ~$30_{-3}^{+5}$ days. Using the magnetic features, the equatorial rotation rate, $\Omega_{eq}$, was found to be 4.51 +/- 0.01 rad/d, with a photospheric shear $\delta\Omega$ of 0.24 +/- 0.03 rad/d. This differential rotation is approximately 4 times that observed on the Sun.