Transit Timing Variations in the three-planet system: TOI-270
Creators: name: Kaye, Laurel
name: Vissapragada, Shreyas
name: Gunther, Maximilian N.
name: Aigrain, Suzanne
name: Mikal-Evans, Thomas
name: Jensen, Eric L. N.
name: Parviainen, Hannu
name: Pozuelos, Francisco J.
name: Abe, Lyu
name: Acton, Jack S.
name: Agabi, Abdelkrim
name: Alves, Douglas R.
name: Anderson, David R.
name: Armstrong, David J.
name: Barkaoui, Khalid
name: Barragan, Oscar
name: Benneke, Bjorn
name: yd, Patricia T. Bo
name: Brahm, Rafael
name: Bruni, Ivan
name: Bryant, Edward M.
name: Burleigh, Matthew R.
name: Casewell, Sarah L.
name: Ciardi, David
name: Cloutier, Ryan
name: Collins, Karen A.
name: Collins, Kevin I.
name: Conti, Dennis M.
name: Crossfield, Ian J. M.
name: Crouzet, Nicolas
name: Daylan, Tansu
name: Dragomir, Diana
name: Dransfield, Georgina
name: abrycky, Daniel F
name: Fausnaugh, Michael
name: Fuuresz, Gabor
name: Gan, Tianjun
name: Gill, Samuel
name: Gillon, Michael
name: Goad, Michael R
name: Gorjian, Varoujan
name: Greklek-McKeon, Michael
name: Guerrero, Natalia
name: Guillot, Tristan
name: Jehin, Emmanuel
name: Jenkins, J. S.
name: Lendl, Monika
name: Kamler, Jacob
name: Kane, Stephen R.
name: Kielkopf, John F.
name: Kunimoto, Michelle
name: Marie-Sainte, Wenceslas
name: McCormac, James
name: Mekarnia, Djamel
name: Morales, Farisa Y.
name: Moyano, Maximiliano
name: Palle, Enric
name: Parmentier, Vivien
name: Relles, Howard M.
name: Schmider, Francois-Xavier
name: Schwarz, Richard P.
name: Seager, S.
name: Smith, Alexis M. S.
name: Tan, Thiam-Guan
name: Taylor, Jake
name: Triaud, Amaury H. M. J.
name: Twicken, Joseph D.
name: Udry, Stephane
name: Vines, J. I.
name: Wang, Gavin
name: Wheatley, Peter J.
name: Winn, Joshua N.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We present ground and space-based photometric observations of TOI-270 (L231-32), a system of three transiting planets consisting of one super-Earth and two sub-Neptunes discovered by TESS around a bright (K-mag=8.25) M3V dwarf. The planets orbit near low-order mean-motion resonances (5:3 and 2:1), and are thus expected to exhibit large transit timing variations (TTVs). Following an extensive observing campaign using 8 different observatories between 2018 and 2020, we now report a clear detection of TTVs for planets c and d, with amplitudes of $\sim$10 minutes and a super-period of $\sim$3 years, as well as significantly refined estimates of the radii and mean orbital periods of all three planets. Dynamical modeling of the TTVs alone puts strong constraints on the mass ratio of planets c and d and on their eccentricities. When incorporating recently published constraints from radial velocity observations, we obtain masses of $M_{\mathrm{b}}=1.48\pm0.18\,M_\oplus$, $M_{c}=6.20\pm0.31\,M_\oplus$ and $M_{\mathrm{d}}=4.20\pm0.16\,M_\oplus$ for planets b, c and d, respectively. We also detect small, but significant eccentricities for all three planets : $e_\mathrm{b} =0.0167\pm0.0084$, $e_{c} =0.0044\pm0.0006$ and $e_{d} = 0.0066\pm0.0020$. Our findings imply an Earth-like rocky composition for the inner planet, and Earth-like cores with an additional He/H$_2$O atmosphere for the outer two. TOI-270 is now one of the best-constrained systems of small transiting planets, and it remains an excellent target for atmospheric characterization.
description: 22 pages, 7 figures