The magnetic field of evolved hot stars

TL;DR

This paper discusses the discovery and analysis of magnetic fields in evolved hot stars, aiming to understand the evolution of fossil magnetic fields and their effects on stellar evolution.

Contribution

It reports the identification of seven evolved magnetic hot stars and suggests the coexistence of fossil and dynamo magnetic fields in these stars.

Findings

Seven evolved magnetic hot stars are now known.

Magnetic field strengths are consistent with flux conservation.

The survey indicates a possible coexistence of fossil and dynamo fields.

Abstract

About 10% of hot stars host a fossil magnetic field on the pre-main sequence and main sequence. However, the first magnetic evolved hot stars have been discovered only recently. An observing program has been set up to find more such objects. This will allow us to test how fossil fields evolve, and the impact of magnetism on stellar evolution. Already 7 evolved magnetic hot stars are now known and the rate of magnetic discoveries in the survey suggests that they host dynamo fields in addition to fossil fields. Finally, the weakness of the measured fields is compatible at first order with simple magnetic flux conservation, although the current statistics cannot exclude intrinsic decay or enhancement during stellar evolution.