Investigating Stellar Evolution: Dynamical Mass Measurements for Gas-Bearing Debris Disk Host Stars

To infer the masses of stars, astronomers typically rely on photospheric measurements of luminosity and effective temperature, interpreted through stellar evolution models. However, with the unprecedented accuracy and precision of distance measurements provided by Gaia, combined with the angular resolution of the Atacama Large Millimeter/submillimeter Array (ALMA), it is now possible to make direct dynamical mass measurements of stars that host circumstellar gas disks.  These dynamical mass measurements leverage Kepler’s third law to derive the stellar mass based on the measured orbital velocity of gas as a function of distance from the host star.  The dynamical mass can then be compared with the mass derived from photospheric properties to test stellar evolution models.  Here we derive dynamical masses for a sample of 15 young gas-bearing debris disk host stars, which represent an older, more massive, and more isolated stellar population than the protoplanetary disk host stars previous studies focused on.  We model the archival molecular gas spectral line emission in the CO J=2−1 or J=3-2 transitions using a ray-tracing code that assumes LTE and hydrostatic equilibrium (Flaherty et al. 2015), and compare our models directly with the visibilities using GALARIO (Tazzari et al. 2018).  We use the MESA Isochrones and Stellar Tracks (MIST) database to compare our derived dynamical masses with expectations based on the photospheric properties.