Letters of Intent received in 2013

LoI 2015-219
Focus Meeting: Magnetic fields and related physics of massive stars

Topics

Observed properties of magnetic fields of massive stars
Structure of magnetic fields and magnetospheres of magnetic massive stars
Origin, generation and evolution of magnetic fields of massive stars
Physics of the wind-field interaction, including plasma/particle physics in massive-star magnetospheres (leading to radio emission, high-energy emission), magnetospheric mass balance and heating/cooling mechanisms
Interplay between magnetic fields and pulsations in massive stars, including synergies between spectropolarimetry and asteroseismology to probe the internal dynamics in massive stars
Influence of magnetic fields on evolution of massive stars, including modification of bulk rotation, influence on internal transport of angular momentum and mixing, consequences for nucleosynthesis, SN progenitors and the related yields, and role of magnetic fields in determining stellar end-states (e.g. magnetars)
Magnetic fields of massive stars at the pre-main sequence and earlier formative stages
Signatures of fossil fields in wind-blown bubbles & SN remnants
Binarity and magnetism
New techniques/instruments/telescopes for measuring magnetic fields of massive stars

Rationale

Massive stars are the powerhouses of the Milky Way. Even before exploding as violent supernovae that seed the galaxy with heavy elements and help trigger new generations of star formation, their intense luminosity lights up and ionizes the nearby interstellar medium, and drives strong, high- speed stellar wind mass outflows. This mass loss, combined with rapid, sometimes near-critical stellar rotation, can exert a strong, even dominant influence on the formation and evolution of such massive stars, and on their demise as supernovae or GRB-producing hypernovae. But recent advances in observation and theory indicate a third agent – magnetic fields – can also play a key role. During recent years, advances in our observational, theoretical and numerical studies of massive star magnetism have led to significant advances in our understanding of this phenomenon:
- New generations of spectropolarimeters have revealed strong (∼kG), ordered (typically dipole) magnetic fields in a growing subset of massive stars, establishing the incidence and characteristics of magnetic fields throughout a large range of stellar mass;
- The observational properties (chemical peculiarities, variability, emission, rotation) of newly-identified magnetic massive stars have been frequently found to be exotic and extreme, emphasizing the importance of magnetic fields in determining their rotational, atmosphere and wind properties;
- Semi-empirical and numerical hydrostatic, hydrodynamic and magnetohydrodynamical simulations have explored the dynamical interaction of such fields with rotation and mass loss in the stellar magnetosphere, in both 2 and 3 dimensions;
- Numerical simulations and theoretical calculations have examined the configurations and stability of large-scale internal field configurations, leading to the demonstration of the existence of stable large-scale internal field configurations, providing a physical basis for a fossil origin of the magnetic fields observed at the surfaces of massive stars, while 3-D numerical MHD simulations have been leveraged to understand the dynamics of magnetic fields both in massive stars' convective cores (dynamos) and in their radiative envelopes (fossil field relaxation) and their mutual coupling. The possibility of dynamos in stellar radiation zones, and in surface convection zones, has also been studied;
- Synergies between spectropolarimetric and asteroseismic observations (provided by the current generation of space-based photometric missions such as CoRoT, MOST and Kepler, and soon BRITE) have begun to provide a new view of the influence of the magnetic fields on stellar interior physics, including constraints on the transport of angular momentum and related mixing;
- The particular role of magnetic fields in binary systems has begun to be explored, including speculations concerning the generation of massive star magnetic fields in stellar mergers;
- Magnetic fields have been identified in pre=main sequence massive stars, recognized as important agents modifying fragmentation in stellar formation, and of the instability at the origin of the explosion of supernovae.
Notwithstanding these important advances, significant open questions remain concerning the origin of massive star magnetic fields, the basic physical processes implicated in the wind-field interaction, and the impact of magnetic fields on their evolution. We will therefore propose a 2 day Focus Meeting at the Honolulu AGM in order to discuss outstanding issues, current activities and future efforts.