TOI-1695 b: A Keystone Water World Elucidating Radius Valley Emergence Mechanisms Around Early M Dwarfs

Monday 28 Nov 2022, 13:30 → 13:50 Europe/Rome

0/0-3 - Sala Rosino (Dipartimento di Fisica e Astronomia - Edificio ex-Rizzato)

Speakers: Alessandro Ruggieri (Università degli Studi di Padova)

Characterizing the bulk compositions of transiting exoplanets within the M dwarf radius valley (i.e. keystone planets) offers a unique means to establish whether the radius valley emerges from an atmospheric mass loss process or is imprinted by planet formation itself. We present the confirmation of a new keystone planet orbiting an early M dwarf (Ms = 0.513 ± 0.012 M?): TOI-1695 b (P = 3.13 days, Rp = 1.90+0.16 −0.14 R⊕). TOI-1695 b’s radius and orbital period situate the planet between model predictions from thermally-driven mass loss versus gas depleted formation, offering an important test case for radius valley emergence models around early M dwarfs. We confirm the planetary nature of TOI-1695 b based on five sectors of TESS data and a suite of follow-up observations including 49 precise radial velocity measurements taken with the HARPS-N spectrograph. We measure a planetary mass of 6.36 ± 1.00 M⊕, which reveals that TOI-1695 b is inconsistent with a purely terrestrial composition of iron and magnesium silicate, and instead is likely a water-rich planet. Our finding that TOI-1695 b is not terrestrial is inconsistent with the planetary system being sculpted by thermally driven mass loss. We also present a statistical analysis of the seven known keystone planets demonstrating that a thermally-driven mass loss scenario is unlikely for this population. Our findings are consistent with the emerging picture that the M dwarf radius valley originates from planetary formation (i.e. they are born rocky/volatile-rich/gas-enveloped) rather than thermally-driven mass loss processes.

2211.06445.pdf

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