This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
Dr. Brian Chaboyer of Dartmouth College will undertake a theoretical investigation of the structure of M dwarfs, which are unevolved stars like the Sun but with less than half its mass. Observations have indicated for some time that theoretical models are unable to correctly predict the mass-radius relation for M dwarfs found in eclipsing binary systems. The observed radii are found to be systematically larger (by about 10%) than that predicted by theoretical models. Recent work has suggested that this is due to increased magnetic activity in these rapidly rotating stars which are tidally locked to their companions. The research will center on the construction of new models of M dwarfs, building upon previous efforts by critically examining the treatment of convection and incorporating the effects of magnetic fields. The physics of the magnetic fields will be included within the stellar structure equations in a phenomenological fashion and the impact of fields of various topologies and field strengths will be studied. Dr. Chaboyer will also explore the effects that various treatments of convection have on the structure and observed properties of low mass stars. This part of the work will incorporate results from recent hydrodynamical calculations of convection. Finally, he will critically examine the color-effective temperature transformations which are used when comparing the models to observations in order to derive an improved calibration.
M dwarf stars are the most common type of star in the Milky Way galaxy. Recently, astronomers have realized that the first Earth-mass planets around other stars are likely to be found around M dwarfs. The models generated in this study will be made available to general astronomical community. There will be extensive involvement of both undergraduate and graduate students in all aspects of this research. This will include mentoring of first year undergraduate students who will work on this project through the auspices of the Women in Science Project at Dartmouth College. This program is designed to encourage more Dartmouth women to pursue a career in science, math or engineering through early exposure to hands-on research experiences, role modeling and mentoring. Upper-year undergraduates will also be employed as research assistants. Dr. Chaboyer will also continue his involvement with local K-8 schools and the Monteshire Museum of Science located in Norwich, Vermont, to discuss this research with young learners and the public at large.
