# Uncovering the true periods of the young sub-Neptunes orbiting TOI-2076

**Authors:** Hugh P. Osborn, Andrea Bonfanti, Davide Gandolfi, Christina Hedges, Adrien Leleu, Andrea Fortier, David Futyan, Pascal Gutermann, Pierre F. L. Maxted, Luca Borsato, Karen A. Collins, J. Gomes da Silva, Yilen Gómez Maqueo Chew, Matthew J. Hooton, Monika Lendl, Hannu Parviainen, Sébastien Salmon, Nicole Schanche, Luisa M. Serrano, Sergio G. Sousa  
**arXiv:** [2203.03194](https://arxiv.org/abs/2203.03194)  
**Date:** 2022-03-07  
**Summary page:** https://www.summarizepaper.com/en/paper/2203.03194v1/

## Key points

- The TOI-2076 system is a young K-type star with three sub-Neptune planets in orbit.
- Orbits of the two outer planets were previously unconstrained due to only two non-consecutive transits being seen in TESS photometry.
- MonoTools package was used to determine which aliases to follow, followed by space-based and ground-based photometric follow-up of TOI-2076 c and d with CHEOPS, SAINTEX, and LCO telescopes.
- Results revealed a clear detection for TOI-2076 c at $P=21.01538^{+0.00084}_{-0.00074}$ d, ruling out three of the most likely period aliases for TOI 2076 d.
- Ground based photometry further enabled researchers to rule out remaining aliases and confirm the $P=35.12537\pm0.00067$ d alias.
- All three sub Neptunes have radii of $2.518\pm0.036$, $3.497\pm0.043$, and $3.232\pm0.063$ $R_\oplus$.
- Anti correlated TTV signal between planets b and c likely caused by their proximity to the 2:1 resonance, while planets c and d appear close to a 5:3 period commensurability; however model degeneracy meant researchers were unable to retrieve robust TTV masses from these data sets alone.

## Summary

The TOI-2076 system is a young ($340\pm80$ Myr) K-type star with three sub-Neptune planets in orbit. While the planetary system has been validated, the orbits of the two outer planets were previously unconstrained due to only two non-consecutive transits being seen in TESS photometry. This led to 11 and 7 possible period aliases for each planet. The aim of this study was to reveal the true orbits of these long-period planets through precise photometry targeted on the highest-probability period aliases, as well as using long-term monitoring of transits in multi-planet systems to constrain planetary masses through TTV measurements. To achieve this goal, the MonoTools package was used to determine which aliases to follow, followed by space-based and ground-based photometric follow-up of TOI-2076 c and d with CHEOPS, SAINTEX, and LCO telescopes. The results revealed a clear detection for TOI-2076 c at $P=21.01538^{+0.00084}_{-0.00074}$ d, ruling out three of the most likely period aliases for TOI 2076 d. Ground based photometry further enabled researchers to rule out remaining aliases and confirm the $P=35.12537\pm0.00067$ d alias. In addition to revealing the true periods of these planets, these observations also improved their radius precision: all three sub Neptunes have radii of $2.518\pm0.036$, $3.497\pm0.043$, and $3.232\pm0.063$ $R_\oplus$. The observations also revealed a clear anti correlated TTV signal between planets b and c likely caused by their proximity to the 2:1 resonance, while planets c and d appear close to a 5:3 period commensurability; however model degeneracy meant researchers were unable to retrieve robust TTV masses from these data sets alone.