The magnetic fields in Be stars are stronger than previously suggested

TL;DR

This study provides the first observational evidence that magnetic fields in Be stars can be significantly stronger than previously thought, with measurements reaching several hundred gauss.

Contribution

It demonstrates that magnetic fields in Be stars are stronger than earlier reports suggested, challenging existing assumptions about their magnetic properties.

Findings

Magnetic fields in all studied Be stars were detected.

The strongest magnetic field measured was about -460 G.

Magnetic fields between 338 and 380 G were found in three other Be stars.

Abstract

Recent observational studies suggest that Be stars most likely are formed through the process of mass transfer in binary systems. In view of the wide consensus that the origin of the magnetic field in stars with radiative envelopes involves binary interaction processes, searching for magnetic fields in Be stars appears especially promising. As a pilot project, we searched for the presence of magnetic fields in a sample of seven well-known Be stars. We used high-resolution HARPSpol spectra to measure the mean longitudinal magnetic field, employing the least squares deconvolution technique. A dedicated measurement procedure introduced by our group in recent years was applied. Opposite to previous spectropolarimetric studies reporting that magnetic fields in Be stars are weak and usually below 100 G, our study presents the first observational evidence that magnetic fields in Be stars can be as strong as a few hundred gauss. Magnetic fields are detected in all studied Be stars, with the strongest magnetic field being about -460 G for the B0.5 III star HD 184915. Magnetic fields in the range between 338 and 380 G (in absolute values) are detected in three other Be stars, HD 209409, HD 209522, and HD 224686. Due to the fact that magnetic fields in Be stars are stronger than previously believed, we must re-evaluate our understanding of the initial conditions of massive binaries to be able to determine the origin of such systems.