A New Spin on M Dwarf Ages and Evolution

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Small, relatively cool stars, less than half the mass of the Sun, are called M dwarf (or red dwarf) stars. These are the most common type of star in the Milky Way. M dwarfs are long-lived, and known to be reliable tracers of the distribution of chemical elements in the Galaxy. They are also the most prolific known hosts of planets, particularly Earth-size planets orbiting in the "habitable zone". A research team at the University of Hawai'i at Manoa will use a combination of new astronomical observations, results from space-based surveys of stars, and computer models of stellar rotation to determine their ages. Accurate ages of M dwarfs will permit tracing distribution of the elements in the Galaxy and will track the planetary environments over Galactic history. Moreover, this research will lead to a better understanding of the rapid rotation and strong magnetic activity of young M dwarfs, which will improve models of their emission of light at many wavelengths, important factors for the environment of any planets that orbit them. The investigators will integrate aspects of this project into an annual program at the University of Hawai'i at Manoa that trains and mentors cohorts of demographically diverse high school students to boost their confidence and understanding of Science, Technology, Engineering, and Mathematics (STEM) subjects and stimulate their interest in STEM-related careers. The students will work with an investigator on a project based on data obtained at a telescope on Mauna Kea and receive ongoing mentoring for six months while they complete their project.The research program seeks to develop a chronometer based on the rotation of M dwarf stars and to study the connections between M dwarf rotation, multiplicity, disks, and pre-main sequence evolution. It will use new observations, results from space-based surveys, and models of stellar rotation to (1) establish a rotational sequence (gyrochrone) of M dwarfs in two solar-aged clusters (M67 and Ruprecht 147) as critical calibration points for spin-down models; (2) produce a mass-rotation diagram for the Hyades, a key intermediate bench-mark for M dwarf spin-down models, which is uniformly and more thoroughly vetted for binaries; (3) confirm or refute a correlation between stellar companions and rotation among pre-main sequence M dwarfs in the Beta Pictoris Moving Group as a test of the disk-locking scenario; and (4) measure masses, radii, luminosities, and magnetic fields of components in selected M dwarf binaries to quantify the effect of rotation and magnetic activity on pre-main sequence evolution.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.