Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Transmission Spectroscopy

Kuzuhara, Masayuki; Fukui, Akihiko; Livingston, John H.; Caballero, José A.; de Leon, Jerome P.; Hirano, Teruyuki; Kasagi, Yui; Murgas, Felipe; Narita, Norio; Omiya, Masashi; Orell-Miquel, Jaume; Palle, Enric; Changeat, Quentin; Esparza-Borges, Emma; Harakawa, Hiroki; Hellier, Coel; Hori, Yasunori; Ikuta, Kai; Ishikawa, Hiroyuki Tako; Kodama, Takanori; Kotani, Takayuki; Kudo, Tomoyuki; Morales, Juan C.; Mori, Mayuko; Nagel, Evangelos; Parviainen, Hannu; Perdelwitz, Volker; Reiners, Ansgar; Ribas, Ignasi; Sanz-Forcada, Jorge; Sato, Bun’ei; Schweitzer, Andreas; Tabernero, Hugo M.; Takarada, Takuya; Uyama, Taichi; Watanabe, Noriharu; Zechmeister, Mathias; García, Néstor Abreu; Aoki, Wako; Beichman, Charles; Béjar, Víctor J. S.; Brandt, Timothy D.; Calatayud-Borras, Yéssica; Carleo, Ilaria; Charbonneau, David; Collins, Karen A.; Currie, Thayne; Doty, John P.; Dreizler, Stefan; Fernández-Rodríguez, Gareb; Fukuda, Izuru; Galán, Daniel; Geraldía-González, Samuel; González-Garcia, Josafat; Hay...

Abstract

Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (P orb) of 12.76 days. The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous P orb from TESS data. We confirmed the transit signal and P orb using ground-based photometry with MuSCAT2 and MuSCAT3, and validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host star is inactive, with an X-ray-to-bolometric luminosity ratio of logLX/Lbol≈−5.7 . Joint analysis of the light curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R ⊕, a 3σ mass upper limit of 3.9 M ⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric (TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.

Citation

Kuzuhara, M., Fukui, A., Livingston, J. H., Caballero, J. A., de Leon, J. P., Hirano, T., Kasagi, Y., Murgas, F., Narita, N., Omiya, M., Orell-Miquel, J., Palle, E., Changeat, Q., Esparza-Borges, E., Harakawa, H., Hellier, C., Hori, Y., Ikuta, K., Ishikawa, H. T., Kodama, T., …Zapatero Osorio, M. R. (2024). Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Transmission Spectroscopy. Astrophysical Journal Letters, 967(2), Article L21. https://doi.org/10.3847/2041-8213/ad3642

• Journal Article Type: Article
• Acceptance Date: Mar 21, 2024
• Online Publication Date: May 23, 2024
• Publication Date: Jun 1, 2024
• Deposit Date: May 28, 2024
• Publicly Available Date: May 28, 2024
• Journal: The Astrophysical Journal Letters
• Print ISSN: 2041-8205
• Electronic ISSN: 2041-8213
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 967
• Issue: 2
• Article Number: L21
• DOI: https://doi.org/10.3847/2041-8213/ad3642
• Keywords: Astronomy data modeling, Exoplanet astronomy, Exoplanets, Exoplanet atmospheres, Space telescopes, High resolution spectroscopy, Radial velocity, Extrasolar rocky planets, Transit photometry
• Public URL: https://keele-repository.worktribe.com/output/833367