Early Results from the HUMDRUM Survey: A Small, Earth-mass Planet Orbits TOI-1450A

Brady, Madison; Bean, Jacob L.; Seifahrt, Andreas; Kasper, David; Luque, Rafael; Stefánsson, Guđmundur; Stürmer, Julian; Charbonneau, David; Collins, Karen A.; Doty, John P.; Essack, Zahra; Fukui, Akihiko; Horta, Ferran Grau; Hedges, Christina; Hellier, Coel; Jenkins, Jon M.; Narita, Norio; Quinn, Samuel N.; Shporer, Avi; Schwarz, Richard P.; Seager, Sara; Stassun, Keivan G.; Striegel, Stephanie; Watkins, Cristilyn N.; Winn, Joshua N.; Zambelli, Roberto

Abstract

M-dwarf stars provide us with an ideal opportunity to study nearby small planets. The HUnting for M Dwarf Rocky planets Using MAROON-X (HUMDRUM) survey uses the MAROON-X spectrograph, which is ideally suited to studying these stars, to measure precise masses of a volume-limited (<30 pc) sample of transiting M-dwarf planets. TOI-1450 is a nearby (22.5 pc) binary system containing a M3 dwarf with a roughly 3000 K companion. Its primary star, TOI-1450A, was identified by the Transiting Exoplanet Survey Satellite (TESS) to have a 2.04 days transit signal, and is included in the HUMDRUM sample. In this paper, we present MAROON-X radial velocities (RVs) which confirm the planetary nature of this signal and measure its mass at nearly 10% precision. The 2.04 days planet, TOI-1450A b, has R b = 1.13 ± 0.04 R ⊕ and M b = 1.26 ± 0.13 M ⊕. It is the second-lowest-mass transiting planet with a high-precision RV mass measurement. With this mass and radius, the planet’s mean density is compatible with an Earth-like composition. Given its short orbital period and slightly sub-Earth density, it may be amenable to JWST follow-up to test whether the planet has retained an atmosphere despite extreme heating from the nearby star. We also discover a nontransiting planet in the system with a period of 5.07 days and a Msinic=1.53±0.18M⊕ . We also find a 2.01 days signal present in the systems’s TESS photometry that likely corresponds to the rotation period of TOI-1450A’s binary companion, TOI-1450B. TOI-1450A, meanwhile, appears to have a rotation period of approximately 40 days, which is in line with our expectations for a mid-M dwarf.

Citation

Brady, M., Bean, J. L., Seifahrt, A., Kasper, D., Luque, R., Stefánsson, G., …Zambelli, R. (2024). Early Results from the HUMDRUM Survey: A Small, Earth-mass Planet Orbits TOI-1450A. Astronomical Journal, 168(2), Article 67. https://doi.org/10.3847/1538-3881/ad500a

• Journal Article Type: Article
• Acceptance Date: May 15, 2024
• Online Publication Date: Jul 10, 2024
• Publication Date: Aug 1, 2024
• Deposit Date: Jul 15, 2024
• Publicly Available Date: Jul 15, 2024
• Journal: The Astronomical Journal
• Print ISSN: 0004-6256
• Electronic ISSN: 1538-3881
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 168
• Issue: 2
• Article Number: 67
• DOI: https://doi.org/10.3847/1538-3881/ad500a
• Keywords: Extrasolar rocky planets, M dwarf stars
• Public URL: https://keele-repository.worktribe.com/output/875572
• Publisher URL: https://iopscience.iop.org/article/10.3847/1538-3881/ad500a