K2 spots rotation in the helium star HD144941

TL;DR

This paper reports the detection of complex, periodic brightness variations in the helium star HD144941 using K2 data, suggesting surface spots caused by magnetic activity and revealing its rotation period.

Contribution

It presents the first detection of rotational variability and surface inhomogeneities in HD144941, a rare helium star, using space-based photometry.

Findings

Detected 13.9-day rotation period.

Observed complex, periodic brightness variations.

Proposed magnetic spots cause surface inhomogeneity.

Abstract

HD144941 is an evolved early-type metal-poor low-mass star with a hydrogen-poor surface. It is frequently associated with other intermediate helium-rich subdwarfs and extreme helium stars. Previous photometric studies have failed to detect any variability. New observations with the K2 mission show complex but periodic variations with a full amplitude of 4 parts per thousand. It is proposed that these are due to an inhomogeneous surface brightness distribution (spots) superimposed on a rotation period of 13.9+/-0.2 d. The cause of the surface inhomogeneity is not identified, although an oblique dipolar magnetic field origin is plausible.