Discovery of fossil magnetic fields in the intermediate-mass pre-main sequence stars

TL;DR

This paper presents observational evidence supporting the hypothesis that magnetic fields in intermediate-mass pre-main sequence stars are fossil remnants rather than generated by dynamo processes, challenging current understanding of stellar magnetism.

Contribution

The study provides strong observational evidence that magnetic fields in intermediate-mass pre-main sequence stars are fossil in origin, not generated by dynamo mechanisms.

Findings

Strong magnetic fields observed in pre-main sequence stars

Magnetic fields are organized and mainly dipolar

Supports fossil origin hypothesis for stellar magnetic fields

Abstract

It is now well-known that the surface magnetic fields observed in cool, lower-mass stars on the main sequence (MS) are generated by dynamos operating in their convective envelopes. However, higher-mass stars (above 1.5 Msun) pass their MS lives with a small convective core and a largely radiative envelope. Remarkably, notwithstanding the absence of energetically-important envelope convection, we observe very strong (from 300 G to 30 kG) and organised (mainly dipolar) magnetic fields in a few percent of the A and B-type stars on the MS, the origin of which is not well understood. In this poster we propose that these magnetic fields could be of fossil origin, and we present very strong observational results in favour of this proposal.