Strong magnetic fields detected in the cores of 11 red giant stars using gravity-mode period spacings

TL;DR

This study detects strong magnetic fields in the cores of 11 red giant stars using gravity-mode period spacings, revealing their influence on stellar oscillation patterns and core wave propagation.

Contribution

It demonstrates the presence of strong magnetic fields in red giant cores and links these fields to observed seismic anomalies, providing new insights into stellar interior magnetism.

Findings

Lower limits on core magnetic fields range from 40 to 610 kG.

Magnetic fields explain deviations from expected gravity-mode period spacings.

One star's magnetic field exceeds the critical threshold, affecting wave propagation.

Abstract

Despite their importance in stellar evolution, little is known about magnetic fields in the interior of stars. The recent seismic detection of magnetic fields in the core of several red giant stars has given measurements of their strength and information on their topology. We revisit the puzzling case of hydrogen-shell burning giants that show deviations from the expected regular period spacing of gravity modes. These stars also tend to have a too low measured period spacing compared to their counterparts. We here show that these two features are well accounted for by strong magnetic fields in the cores of these stars. For 11 Kepler red giants showing these anomalies, we place lower limits on the core field strengths ranging from 40 to 610 kG. For one star, the measured field exceeds the critical field above which gravity waves no longer propagate in the core. We find that this star shows mixed mode suppression at low frequency, which further suggests that this phenomenon might be related to strong core magnetic fields.