Breaking Degeneracies in Stellar Surface Mapping with Astrometry
Jamila Taaki
University of Michigan

Astrometry is a promising technology to both find and measure the masses ofterrestrial-sized exoplanets, orbiting in the habitable zones of sun-likestars. A limitation of the astrometric technique is stellar jitter noise:as a star rotates, starspots may come in and out of view, changing themeasured photo-center. In this talk, I describe how astrometric signalsfrom rotating, spotted stars encode surface-brightness information that canbe used to reconstruct stellar surfaces. Our key result is that astrometryand photometry probe complementary measurement spaces, and that theirjoint use improves the conditioning and identifiability of stellar-surfacemapping. By casting the forward model in a spherical-harmonic basis,we derive analytic expressions for photo-center motion as a functionof stellar surface coefficients and the unknown stellar inclination,allowing us to jointly estimate these quantities. With astrometricmapping of the stellar surface, we can disentangle starspot induced biasfrom exoplanetary signals, bringing us closer to the sub micro-arcsecondastrometric precision where an Earth-mass exoplanet signal lies. --------*

Date:	Mardi, le 25 novembre 2025
Heure:	15:30
Lieu:	Université McGill
	Ernest Rutherford Physics, R.E. Bell Conference Room (room 103)