Kavli Affiliate: David N. Spergel
| First 5 Authors: Daniel A. Yahalomi, Ruth Angus, David N. Spergel, Daniel Foreman-Mackey,
| Summary:
Earth-mass exoplanets on year-long orbits and cool gas giants (CGG) on
decade-long orbits lie at the edge of current detection limits. The Terra
Hunting Experiment (THE) will take nightly radial velocity (RV) observations on
HARPS3 of at least 40 bright nearby G and K dwarfs for 10 years, with a target
1$sigma$ measurement error of $sim$0.3 m/s, in search of exoplanets that are
Earth-like in mass and temperature. However, RV observations can only provide
minimum mass estimates, due to the mass-inclination degeneracy. Astrometric
observations of these same stars, with sufficient precision, could break this
degeneracy. Gaia will soon release $sim$100-200 astrometric observations of
the THE stars with a 10 year baseline and $sim$34.2 $mu$as 1$sigma$
along-scan measurement error. The Nancy Grace Roman Space Telescope will be
capable of precision astrometry using its wide field imager (target $sim$5-20
$mu$as 1$sigma$ measurement error for bright stars) and could extend the
astrometric observational baseline to $sim$25 years. We simulate and model an
observing program that combines data from these three telescopes. We find that
(1) THE RVs and Gaia astrometry can detect Earth-like and CGG-like exoplanets
around bright Sun-like stars at 10 parsecs and that (2) adding Roman astrometry
improves the detection precision for CGG masses and periods by a factor up to
$sim$10 and $sim$4, respectively. Such a survey could provide insight into
the prevalence of Solar System analogs, exoplanet architectures reminiscent of
the mass and orbital separation hierarchy of our Solar System, for the nearest
Sun-like stars.
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