Speaker
Description
Dark magnetic starspots are ubiquitous on the surfaces of cool stars; however, it has been difficult to directly measure magnetic signatures for large stellar samples. We recently showed that spectroscopic starspot filling fractions can be measured in bulk using a two-temperature technique on APOGEE spectra. The resultant precise starspot measurements follow other activity scalings with Rossby number once cleaned of binaries, which implies a dynamo origin. We demonstrate a genuine spot coverage and magnetic field strength saturation in the Pleiades open cluster. In the Praesepe open cluster, we see a strong starspot enhancement feature in stars that are also experiencing stalled spin down. This magnetic enhancement appears to be evidence of a radial shear dynamo, a dynamo mode driven by strong velocity shears in the stellar interior—an effect which may last billions of years and strongly affect the magnetic and rotational evolution of cool stars. Applying a second temperature component to spectroscopic fits in the infrared also yields better fits for heavily spotted stars, resulting in an activity-dependent temperature and radius systematic relative to the non-spotted ASPCAP solution; we describe the role of starspots in producing more accurate and precise stellar masses and radii estimates for large populations of cool stars. We present the first LEOPARD catalog of dwarf starspot fractions for ~135,000 stars, and explore Milky Way Mapper’s potential in extending this discovery sample to a companion magnetic toolkit for stellar and exoplanetary astrophysics.
