A Second Planet Transiting LTT 1445A and a Determination of the Masses of Both Worlds
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Winters_2022_AJ_163_168.pdf
Description
Published version
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18.36 MB
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Adobe PDF
Checksum (MD5)
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Author(s)
Vanderburg, Andrew
Date Issued
April 1, 2022
Journal
The Astronomical Journal
Publisher
American Astronomical Society
Citation
Vanderburg, Andrew. 2022. "A Second Planet Transiting LTT 1445A and a Determination of the Masses of Both Worlds." The Astronomical Journal, 163 (4).
Version
Final published version
Abstract
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 Me) 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 -
+
1.304 0.060
0.067 R⊕, consistent with an Earth-like composition. For the newly
discovered LTT 1445Ac, we measure a mass of -
+
1.54 0.19
0.20 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 Me) is
likely the source of the 1.4 day rotation period, and star B (0.215 Me) 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
MIT Department
Massachusetts Institute of Technology. Department of Physics
MIT Kavli Institute for Astrophysics and Space Research
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Creative Commons Attribution 4.0 International License
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.3847/1538-3881/ac50a9
