Dartmouth Events

Title: Precision radial velocities (RVs) have transformed substellar science, but the mass-inclination degeneracy still limits our ability to fully characterize long-period companions. Over the last decade, the Hipparcos-Gaia Catalog of Accelerations (HGCA)  has enabled absolute astrometric constraints that complement the line-of-sight motion measured by RVs. When combined with RVs, these astrometric accelerations break longstanding degeneracies to deliver model-independent dynamical masses and well-constrained orbital architectures. In this talk, I will review the current landscape of companion detection and characterization across RVs, imaging, and HGCA astrometry. I will then present results from a volume-limited survey of 206 accelerating stars within 20 pc. Among these, we derive new orbital solutions and dynamical masses for nearly 70 systems, primarily stellar binaries but also including several new brown dwarf companions. Combining these results with previously published systems yields a volume-limited framework for companions detectable via HGCA astrometry, from which we draw population-level inferences, such as how the companion mass function varies with host mass. With dynamical masses, the substellar companions will serve as calibration anchors for evolutionary models, and some even as prime targets for atmospheric characterization with JWST. I will also show how our survey’s incompleteness can guide RV and direct imaging campaigns. I will conclude with a look ahead toward Gaia DR4, outlining how this forthcoming data release, coupled with extreme precision RV programs and the launch of the Roman Space Telescope, will extend dynamical mass measurements to cooler hosts and lower-mass companions. These advances will link today’s discoveries to the next decade of direct imaging and population studies of planetary systems and companion formation.

Hosted By Professor Elisabeth Newton 

Zoom Meeting Link: https://dartmouth.zoom.us/j/93069806358