Exoplanets & Exomoons

Masses, Revised Radii, and a Third Planet Candidate in the “Inverted” Planetary System Around TOI-1266

By Keith Cowing
Status Report
October 24, 2023
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Masses, Revised Radii, and a Third Planet Candidate in the “Inverted” Planetary System Around TOI-1266
Individual components of our 3-planet RV model of TOI-1266 and corresponding GLS periodograms. From top to bottom: the raw LBL RVs, stellar RV activity, TOI-1266 b, TOI-1266 c, the planet candidate TOI-1266 d, and the residuals. The residuals do not show any evidence for unaccounted periodicities in the GLS. The vertical shaded regions in the left column highlight each TESS sector’s observing window (annotated at the top) and reveals where we have contemporaneous TESS and spectroscopic observations. Similarly, the vertical dashed lines highlight the epochs of our ground-based transit observations of either TOI-1266 b or c, using the ARCTIC and WIRC cameras. The vertical dashed lines in the right column depict the orbital periods of the transiting TOI-1266 planets, the candidate planet d, and the stellar rotation period inferred from our 𝐻 𝛼 time series. — astro-ph.EP

Is the population of close-in planets orbiting M dwarfs sculpted by thermally driven escape or is it a direct outcome of the planet formation process? A number of recent empirical results strongly suggest the latter.

However, the unique architecture of the TOI-1266 planetary system presents a challenge to models of planet formation and atmospheric escape given its seemingly “inverted” architecture of a large sub-Neptune (Pb=10.9 days, Rp,b=2.62±0.11R⊕) whose orbit is interior to that of the system’s smaller planet (Pc=18.8 days, Rp,c=2.13±0.12R⊕).

Here we present revised planetary radii based on new TESS and diffuser-assisted ground-based transit observations and characterize both planetary masses using a set of 145 radial velocity (RV) measurements from HARPS-N (Mp,b=4.23±0.69M⊕,Mp,c=2.88±0.80M⊕).

Our RV analysis also reveals a third planet candidate (Pd=32.3 days, Mp,dsini=4.59+0.96−0.94M⊕), which if real, would form a chain of 5:3 period ratios, although we show that the system is likely not in a mean motion resonance.

Our results indicate that TOI-1266 b and c are the lowest density sub-Neptunes known around M dwarfs and may exhibit distinct bulk compositions of a gas-enveloped terrestrial (Xenv,b=5.5±0.7%) and a water-rich world (WMFc=59±14%), which is supported by hydrodynamic escape models.

If distinct bulk compositions for the transiting planets are confirmed by atmospheric characterization, the system’s unique architecture would represent an interesting test case for sub-Neptune formation models such as inside-out planet formation at pebble traps.

Ryan Cloutier, Michael Greklek-McKeon, Serena Wurmser, Collin Cherubim, Erik Gillis, Andrew Vanderburg, Sam Hadden, Charles Cadieux, Étienne Artigau, Shreyas Vissapragada, Annelies Mortier, Mercedes López-Morales, David W. Latham, Heather Knutson, Raphaëlle D. Haywood, Enric Pallé, René Doyon, Neil Cook, Gloria Andreuzzi, Massimo Cecconi, Rosario Cosentino, Adriano Ghedina, Avet Harutyunyan, Matteo Pinamonti, Manu Stalport, Mario Damasso, Federica Rescigno, Thomas G. Wilson, Lars A. Buchhave, David Charbonneau, Andrew Collier Cameron, Xavier Dumusque, Christophe Lovis, Michel Mayor, Emilio Molinari, Francesco Pepe, Giampaolo Piotto, Ken Rice, Dimitar Sasselov, Damien Ségransan, Alessandro Sozzetti, Stéphane Udry, Chris A. Watson

Comments: 21 pages. Submitted to MNRAS. Our spectroscopic time series are included in the source files as table6.csv
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2310.13496 [astro-ph.EP] (or arXiv:2310.13496v1 [astro-ph.EP] for this version)
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Submission history
From: Ryan Cloutier
[v1] Fri, 20 Oct 2023 13:43:41 UTC (4,652 KB)


Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻