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TOI-1452 b: SPIRou and TESS Reveal a Super-Earth in a Temperate Orbit Transiting an M4 Dwarf

C. Cadieux, R. Doyon, M. Plotnykov, G. Hébrard, F. Jahandar, E. Artigau, D. Valencia, N. J. Cook, E. Martioli, T. Vandal, J.-F. Donati, R. Cloutier, N. Narita, A. Fukui, T. Hirano, F. Bouchy, N. B. Cowan, E. J. Gonzales, D. Ciardi, K. G. Stassun, L. Arnold, B. Benneke, I. Boisse, X. Bonfils, A. Carmona, P. Cortés-Zuleta, X. Delfosse, T. Forveille, P. Fouqué, J. Gomes da Silva, J. M. Jenkins, F. Kiefer, Á. Kóspál, D. Lafrenière, J. H. C. Martins, C. Moutou, J. D. do Nascimento Jr., M. Ould-Elhkim, S. Pelletier, J. D. Twicken, L. G. Bouma, S. M. Cartwright, A. Darveau-Bernier, K. N. Grankin, M. Ikoma, T. Kagetani, K. Kawauchi, T. Kodama, T. Kotani, D. W. Latham, K. Menou, G. R. Ricker, S. Seager, M. Tamura, R. K. Vanderspek, N. Watanabe

Exploring the properties of exoplanets near or inside the radius valley provides insight on the transition from the rocky super-Earths to the larger, hydrogen-rich atmosphere mini-Neptunes. Here, we report the discovery of TOI-1452b, a transiting super-Earth (Rp = 1.67 ± 0.07 R) in an 11.1 day temperate orbit (Teq = 326 ± 7 K) around the primary member (H = 10.0, Teff = 3185 ± 50 K) of a nearby visual-binary M dwarf. The transits were first detected by the Transiting Exoplanet Survey Satellite, then successfully isolated between the two 3.″2 companions with ground-based photometry from the Observatoire du Mont-Mégantic and MuSCAT3. The planetary nature of TOI-1452b was established through high-precision velocimetry with the near-infrared SPIRou spectropolarimeter as part of the ongoing SPIRou Legacy Survey. The measured planetary mass (4.8 ± 1.3 M) and inferred bulk density (5.6+1.8−1.6 g cm-3) is suggestive of a rocky core surrounded by a volatile-rich envelope. More quantitatively, the mass and radius of TOI-1452b, combined with the stellar abundance of refractory elements (Fe, Mg, and Si) measured by SPIRou, is consistent with a core-mass fraction of 18% ± 6% and a water-mass fraction of 22+21−13 %. The water world candidate TOI-1452b is a prime target for future atmospheric characterization with JWST, featuring a transmission spectroscopy metric similar to other well-known temperate small planets such as LHS 1140b and K2-18 b. The system is located near Webb's northern continuous viewing zone, implying that is can be followed at almost any moment of the year.

Exoplanets; Super Earths; M dwarf stars

The Astronomical Journal
Volume 164, Number 3
2022 September

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia