Observations of Cool-Star Magnetic Fields

By A. Reiners. 2012

177 citations recorded by the source corpus.

Cool stars like the Sun harbor convection zones capable of producing substantial surface magnetic fields leading to stellar magnetic activity. The influence of stellar parameters like rotation, radius, and age on cool-star magnetism, and the importance of the shear layer between a radiative core and the convective envelope for the generation of magnetic fields are keys for our understanding of low-mass stellar dynamos, the solar dynamo, and also for other large-scale and planetary dynamos. Our observational picture of cool-star magnetic fields has improved tremendously over the last years. Sophisticated methods were developed to search for the subtle effects of magnetism, which are difficult to detect particularly in cool stars. With an emphasis on the assumptions and capabilities of modern methods used to measure magnetism in cool stars, I review the different techniques available for magnetic field measurements. I collect the analyses on cool-star magnetic fields and try to compare results from different methods, and I review empirical evidence that led to our current picture of magnetic fields and their generation in cool stars and brown dwarfs.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/954fdf21466cdd8d0cd89aef15e2e585df24ef9f

How researchers see this paper

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In Astronomy and Astrophysics

1. A. Reiners
2. C. Bell
3. Eric Mamajek
4. T. Gastine
5. J. Morin
6. R. Yadav
7. S. Marsden
8. S. Jeffers

In Atomic and Molecular Physics, and Optics

1. Eric Mamajek
2. C. Bell
3. A. Reiners
4. Johannes Wicht

In Instrumentation

1. C. Bell
2. A. Reiners
3. Eric Mamajek
4. J. Morin
5. S. Marsden
6. C. Folsom
7. G. Feiden
8. M. Pecaut

Citations in the corpus

• A BCool magnetic snapshot survey of solar-type stars (2013, background): “Observations of Stokes I and V have shown that typical values for the ratio between the full average field (from Stokes I) and the large scale field (Stokes V) are on the order of 10% or lower (Reiners 2012; Reiners et al. 2009).”
• Stellar magnetism: empirical trends with age and rotation (2014, background): “Indicators of magnetic activity, such as surface spot coverage, emission from the chromosphere, transition region or corona, have been recognised to be closely linked to rotation (e.g., S72; Vilhu 1984; Noyes et al. 1984; Ayres 1997; Guedel 2007; Gondoin 2012; Reiners 2012).”
• On the age of the β Pictoris moving group (2014, background): “Literature measurements for surface magnetic fields on pre-MS F- and G-type stars are extremely sparse and suggest field strengths of less than 1 kG (see e.g. Reiners 2012).”
• From solar-like to antisolar differential rotation in cool stars (2013, background): “For main and pre-main sequence stars, observations of absolutesurface shear show some dependence on rotation period and effective temperature (Barnes et al. 2005; Ammler-von Eiff & Reiners 2012; Reinhold et al. 2013).”