Could the Magnetic Star HD 135348 Possess a Rigidly Rotating Magnetosphere?

TL;DR

This study investigates whether the magnetic star HD 135348 has a rigidly rotating magnetosphere by combining photometric TESS data and spectropolarimetric observations, highlighting the potential of TESS for identifying magnetic stars.

Contribution

The paper presents the first characterization of HD 135348 as a potential RRM star using combined photometric and spectropolarimetric data, and explores machine learning for identifying similar stars.

Findings

HD 135348 likely hosts a centrifugal magnetosphere.

Spectropolarimetric data show a magnetic field consistent with RRM stars.

Lack of typical emission profiles may be due to limited rotational phase coverage.

Abstract

We report the detection and characterization of a new magnetospheric star, HD 135348, based on photometric and spectropolarimetric observations. The TESS light curve of this star exhibited variations consistent with stars known to possess rigidly rotating magnetospheres (RRMs), so we obtained spectropolarimetric observations using the Robert Stobie Spectrograph (RSS) on the Southern African Large Telescope (SALT) at four different rotational phases. From these observations, we calculated the longitudinal magnetic field of the star $\langle B_z \rangle$, as well as the Alfv\'en and Kepler radii, and deduced that this star contains a centrifugal magnetosphere. However, an archival spectrum does not exhibit the characteristic "double-horned" emission profile for H$\alpha$ and the Brackett series that has been observed in many other RRM stars. This could be due to the insufficient rotational phase coverage of the available set of observations, as the spectra of these stars significantly vary with the star's rotation. Our analysis underscores the use of TESS in photometrically identifying magnetic star candidates for spectropolarimetric follow-up using ground-based instruments. We are evaluating the implementation of a machine learning classifier to search for more examples of RRM stars in TESS data.