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

Cadieux, Charles; Doyon, René; Plotnykov, Mykhaylo; Hébrard, Guillaume; Jahandar, Farbod; Artigau, Étienne; Valencia, Diana; Cook, Neil J.; Martioli, Eder; Vandal, Thomas; Donati, Jean-François; Cloutier, Ryan; Narita, Norio; Fukui, Akihiko; Hirano, Teruyuki; Bouchy, François; Cowan, Nicolas B.; Gonzales, Erica J.; Ciardi, David R.; Stassun, Keivan G.; Arnold, Luc; Benneke, Björn; Boisse, Isabelle; Bonfils, Xavier; Carmona, Andrés; Cortés-Zuleta, Pía; Delfosse, Xavier; Forveille, Thierry; Fouqué, Pascal; da Silva, João Gomes; Jenkins, Jon M.; Kiefer, Flavien; Kóspál, Ágnes; Lafrenière, David; Martins, Jorge H. C.; Moutou, Claire; do Nascimento, J. -D.; Ould-Elhkim, Merwan; Pelletier, Stefan; Twicken, Joseph D.; Bouma, Luke G.; Cartwright, Scott; Darveau-Bernier, Antoine; Grankin, Konstantin; Ikoma, Masahiro; Kagetani, Taiki; Kawauchi, Kiyoe; Kodama, Takanori; Kotani, Takayuki; Latham, David W.; Menou, Kristen; Ricker, George; Seager, Sara; Tamura, Motohide; Vanderspek, Roland; Watanabe, Noriharu
Bibliographical reference

The Astronomical Journal

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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 (R p = 1.67 ± 0.07 R ⊕) in an 11.1 day temperate orbit (T eq = 326 ± 7 K) around the primary member (H = 10.0, T eff = 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 ( ${5.6}_{-1.6}^{+1.8}$ 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 ${22}_{-13}^{+21}$ %. 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.