A Tale of Two Peas in a Pod: The Kepler-323 and Kepler-104 Systems
Abstract
In order to understand the relationship between planet multiplicity, mass, and composition, we present newly measured masses of five planets in two planetary systems: Kepler-323 and Kepler-104. We used the HIRES instrument at the W.M. Keck Observatory to collect 79 new radial velocity (RV) measurements for Kepler-323, which we combined with 48 literature RVs from TNG/HARPS-N. We also conducted a reanalysis of the Kepler-104 system, using 44 previously published RV measurements. Kepler-323 b and c have masses of 2.0_(−1.1)^(+1.2) M⊕ and 6.5 ± 1.6 M⊕, respectively, whereas the three Kepler-104 planets are more massive (10.0 ± 2.8 M⊕, 7.1_(−3.5)^(+3.8) M⊕, and 5.5_(−3.5)^(+4.6) M_⊕ for planets b, c, and d, respectively). The Kepler-104 planets have densities consistent with rocky cores overlaid with gaseous envelopes (4.1_(−1.1_^(+1.2) g cc−1, 2.9_(−1.5)^(+1.7) g cc−1, and 1.6_(−1.1)^(+1.5) g cc−1 respectively), whereas the Kepler-323 planets are consistent with having rocky compositions (4.5_(−2.4)^(+2.8) g cc−1 and 9.9_(−2.5)^(+2.7) g cc−1). The Kepler-104 system has among the lowest values for gap complexity (𝐶 = 0.004) and mass partitioning (𝑄 = 0.03); whereas, the Kepler-323 planets have a mass partitioning similar to that of the Inner Solar System (𝑄 = 0.28 and 𝑄 = 0.24, respectively). For both exoplanet systems, the uncertainty in the mass partitioning is affected equally by (1) individual mass errors of the planets and (2) the possible existence of undetected low-mass planets, meaning that both improved mass characterization and improved sensitivity to low-mass planets in these systems would better elucidate the mass distribution among the planets.
Copyright and License
© 2024. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Acknowledgement
We acknowledge support in the form of observational resources at W. M. Keck Observatory from NASA and the University of Hawai'i. L.M.W. acknowledges support from the NASA-Keck Key Strategic Mission Support program (grant no. 80NSSC19K1475) and the NASA Exoplanet Research Program (grant no. 80NSSC23K0269).
This work was supported by a NASA Keck PI Data Award, administered by the NASA Exoplanet Science Institute. Data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to the National Aeronautics and Space Administration through the agency's scientific partnership with the California Institute of Technology and the University of California. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. This dataset made use of the NASA Exoplanet Science Institute at IPAC, which is operated by the California Institute of Technology under contract with the National Aeronautics and Space Administration.
We acknowledge contributions from B.J. Fulton for maintaining the Jump database in which data for this project were curated. We acknowledge L. A. Rogers for contributing to the proposals that led to the collection of RVs presented here and for useful discussions and comments on the manuscript.
We would like to thank Greg Gilbert for investigating the presence of TTVs in these systems.
The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
Facilities
Keck:I (HIRES) -
Software References
RADVEL (Fulton et al. 2018)
Files
Thomas_2024_AJ_167_160.pdf
Additional details
Identifiers
- ISSN
- 1538-3881
Funding
- National Aeronautics and Space Administration
- 80NSSC19K1475
- National Aeronautics and Space Administration
- 80NSSC23K0269
- National Aeronautics and Space Administration
- NASA Earth and Space Science and Technology Fellowship
- Princeton University
- Henry Norris Russell Fellowship
- National Aeronautics and Space Administration
- NASA Sagan Fellowship