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Testing the Formation of the M Dwarf Radius Valley with the TESS Multi-planetary System TOI-1730

Presentation #403.10 in the session Exoplanet Transits — iPoster Session.

Published onJun 29, 2022
Testing the Formation of the M Dwarf Radius Valley with the TESS Multi-planetary System TOI-1730

Characterizing multi-planetary systems is essential for understanding the observed exoplanet distribution and can be used to assess models of planet formation. One such system discovered by the Transiting Exoplanet Survey Satellite (TESS) mission in Year 2 is TOI-1730, a system of two close-in planets orbiting an early M dwarf. We validated these two planets using TESS and ground-based transit data, and measured orbital periods of 2.16 days and 6.22 days with planetary radii of 1.4 ± 0.1 R and 2.3 ± 0.1 R. Based on these parameters, the two planets span the radius valley, making the measurement of their bulk compositions of interest for testing physical models for the formation of the radius valley. To this end, we analyzed 43 precise radial velocity measurements from the HARPS-N spectrograph to characterize the bulk compositions of these planets. We measured a preliminary mass of 7.13 -1.35/+1.29 M for the outer planet and an upper limit of 3.73 M on the mass of the inner planet at 95% confidence, and uncovered an anomalous signal at a period of 12-14 days that could not be easily explained by stellar activity, but was potentially indicative of a third planet in the system. This target was revisited by TESS in Year 4, which revealed the existence of a third transiting planet at a 12.6 day period. By updating the RV model to account for three planets and stellar activity, we reconcile the anomalous RV signal and validate this third 12.6 day period planet. The transit and RV analysis of this validated three-planet system is ongoing and will allow us to test the viability of models of atmospheric loss that are important to shaping the population of close-in planets around M dwarfs.

The SAO REU program is funded in part by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant no. AST-2050813, and by the Smithsonian Institution.

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