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Revising the Mass and Radius of a High-Demand JWST super Earth Target

Presentation #601.19 in the session Planet Detection - Radial Velocities.

Published onApr 03, 2024
Revising the Mass and Radius of a High-Demand JWST super Earth Target

The TESS mission continues to provide exoplanet candidates that are promising targets for atmospheric characterization with the Hubble and James Webb Space Telescopes, and increasing effort is being poured into validating and characterizing these new worlds. Given the indirect detection nature of both transit photometry and the radial velocity methods generally used to procure mass measurements, the parameters of the host star play a key role in deriving precise and accurate planet masses and radii, which are necessary to interpret atmospheric spectra. Here we present revisions to the mass and radius of the ultra-short period super-Earth planet, TOI-1685 b. This planet has been featured in two discovery papers and will be observed in three JWST cycle two proposals. The planet’s mass, radius, and bulk density are discrepant between the discovery papers, however, allowing the planet to be interpreted either as a hot, bare rock or a bone fide water world. We have performed a refined stellar classification with a focus on addressing the host star’s metallicity and find the star to be both smaller and less massive than stated in either of the discovery papers. In addition, we carry out an updated transit analysis based on an additional TESS sector and multi-color photometry from all three ground-based MuSCAT instruments, and a new RV analysis based on the previously published CARMENES and IRD data, along with two new semesters of high precision MAROON-X data. From the transit analysis, we derive a planetary radius of 1.468 ± 0.051 Earth radii, and from the RV analysis we measure a planet mass of 3.11 ± 0.33 Earth masses. This combination produces a bulk density of 5.41 ± 0.80 g/cm3, very similar to the Earth’s bulk density of 5.5 g/cm3, which falls in between the previously derived values and suggests that the planet is likely a hot rock and not a water world.

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