Triple-star dynamics and the internal structure of low-mass stars

San Diego State University Foundation, San Diego CA

Investigators

Abstract

This project will study the stars in triple-star systems, which have three stars orbiting a common center of mass. These systems have orbits which cause the stars to eclipse, or move in front of, eachother as seen during observation. The stars' movements will be used to determine their fundamental properties. The project takes advantage of the fact that the stars in a triple-star system are at the same distance from us, which makes it possible to determine their relative sizes. Follow-up spectroscopy of the stars' radial velocities and detailed modeling is used to determine absolute radii. Triple-star systems have very complicated motion, which changes their apparent brightness over time. The team will model these data to determine the internal mass distributions. They will train graduate students working on Master's degrees and undergraduate students working on senior thesis projects. The investigators will also incorporate research results into their college courses and public lectures. The work will be completed by examining, for the first time, the apsidal motion of three-body eclipsing binaries for stars less massive than the Sun. The rate of apsidal precession is related to the mass distribution inside the stars, which the team will model. They will use archival NASA Kepler mission lightcurves (photometric time series) and photo-dynamical computer models to measure the apsidal motion constants, which are directly related to the distribution and concentration of mass inside a star. The constants will be determined by modeling the changes in orbital period of the stars. They will use spectroscopy obtained at multiple ground-based telescopes to measure the radial velocities and determine the standard stellar photospheric characteristics, such as effective temperature, metallicity, surface gravity and rotational velocity. They will make publicly available the datasets and tools they developed to model multiple overlapping eclipse events for the astronomical community, as well as the eclipse times, and radial velocity measurements.