English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

While surface fields have been measured for stars across the HR diagram,internal magnetic fields remain largely unknown. The recent seismic detectionof magnetic fields in the cores of several Kepler red giants has opened a newavenue to understand better the origin of magnetic fields and their impact onstellar structure and evolution. We aim to use asteroseismology tosystematically search for internal magnetic fields in red giant stars and todetermine the strengths and geometries of these fields. Magnetic fields areknown to break the symmetry of rotational multiplets. In red giants,oscillation modes are mixed, behaving as pressure modes in the envelope and asgravity modes in the core. Magnetism-induced asymmetries are expected to bestronger for g-dominated modes than for p-dominated modes and to decrease withfrequency. After collecting a sample of 2500 Kepler red giant stars with clearmixed-mode patterns, we specifically searched for targets among 1200 stars withdipole triplets. We identified 13 stars exhibiting clear asymmetric multipletsand measured their parameters, especially the asymmetry parameter and themagnetic frequency shift. By combining these estimates with best-fittingstellar models, we measured average core magnetic fields ranging from 20 to150kG, corresponding to 5% to 30% of the critical field strengths. We showedthat the detected core fields have various horizontal geometries, some of whichsignificantly differ from a dipolar configuration. We found that the fieldstrengths decrease with stellar evolution, despite the fact that the cores ofthese stars are contracting. Even though these stars have strong internalmagnetic fields, they display normal core rotation rates, suggesting nosignificantly different histories of angular momentum transport compared toother red giant stars. We also discuss the possible origin of the detectedfields.

Internal magnetic fields in 13 red giants detected by asteroseismology