The evolution of magnetic fields in hot stars

Mary E. Oksala(1,2), Coralie Neiner(2), Cyril Georgy(3), Norbert Przybilla(4), Zsolt Keszthelyi(5,6), Gregg Wade(5), Stephane Mathis(7,2), Aurore Blazere(8,2), Bram Buysschaert(2,9)

(1) Department of Physics, California Lutheran University, 60 West Olsen Road #3700, Thousand Oaks, CA 91360, USA; (2) LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universites, UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cite, 5 place Jules Janssen, 92195 Meudon, France; (3) Geneva Observatory, University of Geneva, chemin des Maillettes 51, 1290 Sauverny, Switzerland; (4) Institut fur Astro- und Teilchenphysik, Universitat Innsbruck, Technikerstr. 25/8, 6020, Innsbruck, Austria; (5) Department of Physics, Royal Military College of Canada, PO Box 17000 Station Forces, Kingston, ON K7K 0C6, Canada; (6) Department of Physics, Engineering Physics and Astronomy, Queen'€™s University, 99 University Avenue, Kingston, ON K7L 3N6, Canada; (7) Laboratoire AIM Paris-Saclay, CEA/DRF - CNRS - Universite Paris Diderot, IRFU/SAp Centre de Saclay, 91191 Gif-sur-Yvette, France; (8) Institut d'Astrophysique et de Geophysique, Universite de Liege, Quartier Agora (B5c), Allee du 6 aout 19c, 4000 Sart Tilman, Liege, Belgium; (9) Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium

Over the last decade, tremendous strides have been achieved in our understanding of magnetism in main sequence hot stars. In particular, the statistical occurrence of their surface magnetism has been established (~10%) and the field origin is now understood to be fossil. However, fundamental questions remain: how do these fossil fields evolve during the post-main sequence phases, and how do they influence the evolution of hot stars from the main sequence to their ultimate demise? Filling the void of known magnetic evolved hot (OBA) stars, studying the evolution of their fossil magnetic fields along stellar evolution, and understanding the impact of these fields on the angular momentum, rotation, mass loss, and evolution of the star itself, is crucial to answering these questions, with far reaching consequences, in particular for the properties of the precursors of supernovae explosions and stellar remnants. In the framework of the BRITE spectropolarimetric survey and LIFE project, we have discovered the first few magnetic hot supergiants. Their longitudinal surface magnetic field is very weak but their configuration resembles those of main sequence hot stars. We present these first observational results and propose to interpret them at first order in the context of magnetic flux conservation as the radius of the star expands with evolution. We then also consider the possible impact of stellar structure changes along evolution.

Reference: Proceeding -- IAUS329
Status: Conference proceedings