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A second planet transiting LTT 1445A and a determination of the masses of both worlds

LTT 1445 is a hierarchical triple M-dwarf star system located at a distance of 6.86 pc. The primary star LTT 1445A (0.257 M ⊙) is known to host the transiting planet LTT 1445Ab with an orbital period of 5.36 days, making it the second-closest known transiting exoplanet system, and the closest one fo...

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Main Authors: Winters, Jennifer G. (Author) , Stürmer, Julian (Author) , Cloutier, Ryan (Author) , Medina, Amber A. (Author) , Irwin, Jonathan M. (Author) , Charbonneau, David (Author) , Astudillo-Defru, Nicola (Author) , Bonfils, Xavier (Author) , Howard, Andrew W. (Author) , Isaacson, Howard (Author) , Bean, Jacob L. (Author) , Seifahrt, Andreas (Author) , Teske, Johanna K. (Author) , Eastman, Jason D. (Author) , Twicken, Joseph D. (Author) , Collins, Karen A. (Author) , Jensen, Eric L. N. (Author) , Quinn, Samuel N. (Author) , Payne, Matthew J. (Author) , Kristiansen, Martti H. (Author) , Spencer, Alton (Author) , Vanderburg, Andrew (Author) , Zechmeister, Mathias (Author) , Weiss, Lauren M. (Author) , Wang, Sharon Xuesong (Author) , Wang, Gavin (Author) , Udry, Stéphane (Author) , Terentev, Ivan A. (Author)
Format: Article (Journal)
Language:English
Published: 2022 March 14
In: The astronomical journal
Year: 2022, Volume: 163, Issue: 4, Pages: 1-18
ISSN:1538-3881
DOI:10.3847/1538-3881/ac50a9
Online Access:Verlag, lizenzpflichtig, Volltext: https://doi.org/10.3847/1538-3881/ac50a9
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Author Notes:Jennifer G. Winters, Julian Stürmer [und weitere Verfasser]
Description
Summary:LTT 1445 is a hierarchical triple M-dwarf star system located at a distance of 6.86 pc. The primary star LTT 1445A (0.257 M ⊙) is known to host the transiting planet LTT 1445Ab with an orbital period of 5.36 days, making it the second-closest known transiting exoplanet system, and the closest one for which the host is an M dwarf. Using Transiting Exoplanet Survey Satellite data, we present the discovery of a second planet in the LTT 1445 system, with an orbital period of 3.12 days. We combine radial-velocity measurements obtained from the five spectrographs, Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations, High Accuracy Radial Velocity Planet Searcher, High-Resolution Echelle Spectrometer, MAROON-X, and Planet Finder Spectrograph to establish that the new world also orbits LTT 1445A. We determine the mass and radius of LTT 1445Ab to be 2.87 ± 0.25 M ⊕ and R ⊕, consistent with an Earth-like composition. For the newly discovered LTT 1445Ac, we measure a mass of M ⊕ and a minimum radius of 1.15 R ⊕, but we cannot determine the radius directly as the signal-to-noise ratio of our light curve permits both grazing and nongrazing configurations. Using MEarth photometry and ground-based spectroscopy, we establish that star C (0.161 M ⊙) is likely the source of the 1.4 day rotation period, and star B (0.215 M ⊙) has a likely rotation period of 6.7 days. We estimate a probable rotation period of 85 days for LTT 1445A. Thus, this triple M-dwarf system appears to be in a special evolutionary stage where the most massive M dwarf has spun down, the intermediate mass M dwarf is in the process of spinning down, while the least massive stellar component has not yet begun to spin down.
Item Description:Gesehen am 21.04.2022
Physical Description:Online Resource
ISSN:1538-3881
DOI:10.3847/1538-3881/ac50a9

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