Characterization of the Compact Multiplanet System TOI-789: Validation of Three Terrestrial Planets, Dynamical Characterization, and Detection of a Fourth Temperate Candidate
- 1Independent Researcher, Málaga, ; [email protected]
Abstract
We present the validation and dynamical characterization of TOI-789 (TIC 300710077), a compact multiplanet system around an M3 dwarf at 43 pc. Using ∼7 yr of TESS photometry (42 sectors), public ground-based follow-up (LCOGT, MEarth), and high-resolution imaging (Gemini/Zorro, SOAR), we statistically validate three terrestrial planets with TRICERATOPS: TOI-789 b ( R p = 1.18 R ⊕ , P = 5.45 days), c (1.15 R ⊕ , 8.04 days), and d (1.40 R ⊕ , 12.97 days), with false-positive and nearby-false-positive probabilities below the validation thresholds once resolved neighbours are excluded using the on-target ground-based photometry. Through an iterative Transit Least Squares search we identify a fourth, previously uncatalogued planet candidate ( P = 19.74 days, R p ≈ 0.88 R ⊕ ), the outermost and most temperate member ( S = 1.71 S ⊕ , T eq ≈ 292 K); its low signal-to-noise ratio precludes formal validation, so we report it as a candidate pending confirmation. A dynamical analysis (SPOCK and N -body integrations) indicates a dynamically cold, near-resonant system that is stable only for low eccentricities ( e ≲ 0.05); it is eccentricity rather than planetary mass that limits the system's stability, and including the fourth candidate tightens this constraint further. The four objects span the Earth–Venus transition across the Venus zone, with two validated planets falling in the temperate regime under the equilibrium-temperature criterion, making the system a potential comparative-planetology laboratory anchored on confirmed planets. The low TSM (∼3–5) and moderate host brightness place atmospheric characterization beyond reach. TOI-789 exemplifies the numerically dominant population of compact terrestrial-planet systems around M dwarfs whose characterization is limited by host brightness for which dynamical characterization offers a complementary route.
Versions
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BibTeX
@article{navarrete2026characterization,
title = {{Characterization of the Compact Multiplanet System TOI-789: Validation of Three Terrestrial Planets, Dynamical Characterization, and Detection of a Fourth Temperate Candidate}},
author = {Juan F. Pagés Navarrete},
journal = {The Astronomical Journal},
year = {2026},
month = oct,
doi = {10.3847/1538-3881/aea6c9},
url = {https://iopscience.iop.org/article/10.3847/1538-3881/aea6c9},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Characterization of the Compact Multiplanet System TOI-789: Validation of Three Terrestrial Planets, Dynamical Characterization, and Detection of a Fourth Temperate Candidate
AU - Juan F. Pagés Navarrete
PY - 2026
DA - 2026/10/07
JO - The Astronomical Journal
DO - 10.3847/1538-3881/aea6c9
UR - https://iopscience.iop.org/article/10.3847/1538-3881/aea6c9
AB - We present the validation and dynamical characterization of TOI-789 (TIC 300710077), a compact multiplanet system around an M3 dwarf at 43 pc. Using ∼7 yr of TESS photometry (42 sectors), public ground-based follow-up (LCOGT, MEarth), and high-resolution imaging (Gemini/Zorro, SOAR), we statistically validate three terrestrial planets with TRICERATOPS: TOI-789 b ( R p = 1.18 R ⊕ , P = 5.45 days), c (1.15 R ⊕ , 8.04 days), and d (1.40 R ⊕ , 12.97 days), with false-positive and nearby-false-positive probabilities below the validation thresholds once resolved neighbours are excluded using the on-target ground-based photometry. Through an iterative Transit Least Squares search we identify a fourth, previously uncatalogued planet candidate ( P = 19.74 days, R p ≈ 0.88 R ⊕ ), the outermost and most temperate member ( S = 1.71 S ⊕ , T eq ≈ 292 K); its low signal-to-noise ratio precludes formal validation, so we report it as a candidate pending confirmation. A dynamical analysis (SPOCK and N -body integrations) indicates a dynamically cold, near-resonant system that is stable only for low eccentricities ( e ≲ 0.05); it is eccentricity rather than planetary mass that limits the system's stability, and including the fourth candidate tightens this constraint further. The four objects span the Earth–Venus transition across the Venus zone, with two validated planets falling in the temperate regime under the equilibrium-temperature criterion, making the system a potential comparative-planetology laboratory anchored on confirmed planets. The low TSM (∼3–5) and moderate host brightness place atmospheric characterization beyond reach. TOI-789 exemplifies the numerically dominant population of compact terrestrial-planet systems around M dwarfs whose characterization is limited by host brightness for which dynamical characterization offers a complementary route.
SN - 0004-6256
SN - 1538-3881
ER -