Collaborative Research: Rotational Evolution and Angular Momentum Transport in Deeply Convective Dwarfs

Ohio State University, The, Columbus OH

Investigators

Abstract

Stars, like our Sun, spin more slowly as they get older. This happens because they lose energy through winds and magnetic fields. But scientists have found that certain stars—called K dwarfs—don’t slow down the way we expect. These stars seem to stay active and spin faster than they should, even as they age. This project will help us understand why. The researchers will build new computer models to test how energy and magnetism move inside these stars. They will also use large telescopes to directly measure the magnetic fields of K dwarfs that behave in surprising ways. Understanding how stars age is important for many areas of science, including learning the ages of planets around other stars. This project also supports science education in Hawaii by helping teachers bring real astronomy into their classrooms. By combining new models, detailed observations, and outreach, this project will promote scientific progress and expand opportunities for diverse learners to explore space science. The investigators aim to address the unexpected rotational evolution and persistent magnetic activity observed in K dwarf stars (~3900–5300 K). The project will combine novel internal angular momentum (AM) transport models—including hydrodynamic, gravity wave-driven, and magnetic processes—with modern magnetic braking laws implemented in the Yale Rotating Stellar Evolution Code (YREC). These models will be tested against a wide array of observational constraints, including open cluster rotation sequences, field star rotation periods, magnetic activity proxies, light-element depletion trends, and newly acquired spectropolarimetric data. The observational component will include direct measurements of magnetic field strength and topology in anomalous K dwarfs using PEPSI (LBT), ESPaDOnS (CFHT), and SPIRou (CFHT), focusing on stars in the Hyades cluster. The overarching goals are to improve theoretical understanding of rotational evolution in low-mass stars and to enable more accurate use of gyrochronology in stellar age determinations. The project also supports the development of new astronomy-based curricular tools through the TeachAstro program for middle and high school STEM teachers in Hawaii. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.