Collaborative Research: A Fresh Look at M-Dwarfs from the Bottom Up

Collaborative Research: A Fresh Look at M-Dwarfs from the Bottom Up Collaborative Research: A Fresh Look at M-Dwarfs from the Bottom Up Overview: We propose a thorough modeling study of M dwarf atmospheres, interiors, and evolution. Previous work on M dwarf physics has used methods and codes devised for more massive stars, with workers moving down in mass to M dwarfs. In science a diversity of methods is often important to research progress and understanding. Here we propose to use modeling tools developed for brown dwarfs, just lower in mass than the M stars, and we will move up in mass to model these objects. M dwarfs and brown dwarfs share many similarities. Most importantly both feature molecule-dominated atmospheres and partially degenerate interiors. First, we will pioneer spectral ?retrieval? models for M stars, a fully Bayesian data-driven method to yield best-fit temperature structures and abundances that are not bound to pre-computed atmosphere grids. We will focus on benchmark well-studied M stars in orbit around Sun-like primaries. Second, based on the outcomes in part 1, we will compute a large grid of radiative-convective model atmospheres to yield trends in temperature, gravity, and metallicity, which will be of use to the broad community. Such models will also serve as the upper boundary conditions for our third goal, new self-consistent M dwarf evolution models with MESA, which will include a new hydrogen equation of state. We will pursue detailed comparisons with previous theoretical and observational work on M dwarf atmospheres, their locations on the H-R diagram, and observed mass-radius relations. Intellectual Merit: An understanding of M dwarf atmospheres, structure, and evolution is fundamental to a number of areas of astronomical study. By number M dwarfs dominate the galaxy and the solar neighborhood, as they make over 70% of all stars. A better understanding of their physical properties touches on galactic chemical evolution, the dynamics of the galaxy, stellar atmospheres, molecular astrophysics, star formation, planet formation, and exoplanet characterization. The field could use a diversity in research methods and approaches, and here we aim to do that. Broader Impacts: These projects have an important training component, as nearly all of the proposed work will be for three PhD theses, at UC Santa Cruz, Arizona State University, and Boston University. The PI will involve undergraduates in his research every year. The Co-PIs will create a new stellar astrophysics class and will also create a training session and webinar for students to learn about future careers. The results of this work will be broadly shared with the astronomical community in long-lived repositories such that they can be used by other investigators.